
Class TcTC7^J 

Book - ^ 7 

Copyright ]^°. 



COPYRIGHT DEPOSIT. 



VALVE SETTING 



VALVE SETTING 



SIMPLE METHODS OF 

SETTING THE PLAIN SLIDE VALVE, 

MEYER CUT-OFF, CORLISS, 

AND POPPET TYPES 



COMPILED AND WRITTEN BY 

HUBERT E. COLLINS 



1908 

HILL PUBLISHING COMPANY 

505 PEARL STREET, NEW YORK 

6 BouvEEiE Street, London, E. C. 
Power — American Machinist — The Engineering and Mining Journal 



-l 



K 



A 



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LISRARY of CONGRESS I 
Tv/o Copies Received 

NOV U 1908 

CLASS OJ XXc No, 
COPY 3. 



Copyright, 1908, by the Hill Publishing Company 




Hill PuhlisMng Company, New York, TJ. S. A. 



INTKODUCTION 

SuPEKVisiNG, operating, and erecting engineers have long felt the need 
of a book giving simple, practical instructions in the setting of valves for 
all kinds of engines. Poiver has from time to time published articles cov- 
ering the leading types, and this book is based on the material contributed 
for this series. 

In the main, the articles are secured from builders or erecting men who 
are familiar with the practical work involved, and in every case the work 
has been passed upon and approved by the builders. 

Eecognizing the fact that the fundamental principles of all valve design 
are contained in the slide valve movement, the first three chapters of this 
book are given to a study of this subject. Afterwards a general idea of 
the Meyer valve movement is given and then the Corliss. 

In Chapter IV, written by the compiler of this book, are given general 
rules for finding crank and eccentric centers which can be applied to any 
make of reciprocating engine. These rules are a valuable aid in valve set- 
ting. Careful consideration of the first five chapters will enable a man to 
grasp any other part of the book where special makes of engines are de- 
scribed, and will be highly useful to any man meeting any problem in valve 
setting, whether described in detail in this book or not. 

The compiler of this book is greatly indebted to the following men who 
have contributed material to Power which is embodied in this book: 

E. S. Hawkins, John L. Flock, Thomas Hall, F. L. Johnson, Carl S. 
Dow, F. F. Nickel, Claude Aikens, and E. F. Williams. 

Hubert E. Collins. 

New York, July 1908. 



CONTENTS 

CHAPTER PAGE 

I. The Slide Valve Explained 3 

II. A Study of the D Slide- Valve 19 

III. A Study of the Zeuner Slide-Valve Diagram 29 

IV. The Riding Cut-off Valve 38 

V. The Corliss Steam Engines 53 

VI. The Greene-Wheelock Engine 62 

VII. The Brown Engine 76 

VIII. The McIntosh & Seymour Engine 84 

IX. The Buckeye Engine . . . 92 

X. The Porter-Allen Engine 103 

XI. The Fitchburg Engine Ill 

XII. The Fleming Piston- Valve Engines 121 

XIII. The Putnam Engine 130 

XIV. The Sturtevant Compound Engine 135 

XV. The Rice & Sargent Engine 145 

XVI. Reynolds (1890) and Girder Frame Corliss Engines . . . 152 

XVII. The Wright Steam Engine . . . . . . . . . 159 

XVIII. The Reynolds Long-Range Cut-off 172 

XIX. The Duplex Pump 180 

XX. Air Compressors 188 

INDEX .203 



VALVE SETTING 



THE SLIDE VALVE EXPLAINED 

The simplest form of slide valve is shown in Fig. 1. As will be seen, 
there is neither steam lap, positive exhaust lap, nor negative exhaust lap. 
The valve is shown at the center of its travel, that is, located centrally 
over the ports. The references S P, S P denote the cylinder ports; E P 



/> 



H 

e 2: 






FIG. 1. 



is the exhaust port ; V is the valve ; a a are the steam edges of the valve, 
and h h the exhaust edges ; c c are the exhaust edges, and d d the steam 
edges, of the cylinder port. 

Above the valve are shown the valve circles, one for each end. The 
eccentric position is at e when the crank is at c, at the end of the stroke. 
The eccentric is 90 degrees ahead of the crank when the valve has no lap 
nor lead. When lead is added, the eccentric will be advanced to some posi- 
tion beyond 90 degrees, say to the point x. It will be noted that if lead 
were added, the valve and crank moving in the direction denoted by the 
arrows, the cylinder port on the head end would-be open to the admission 
of steam between the steam edges a and d on that end, and at the same 
time the steam would be exhausting from the other cylinder port through 

3 



4 VALVE SETTING 

the edges h and c on the crank end. In Fig. 1, there being no valve lap, 
the travel of the valve is equal to twice the width of the port. The added 
lead does not change the valve travel, but causes an earlier action, as shown 
by the small diagrams A and B below the circles. Of these, A shows the 
kind of diagram which would result with no lead, while B shows the effect 
of lead. 

Lead and Lap 

Lead, or the angular advance of a valve, is the amount of opening to 
the cylinder port, or the distance between the edges a and d when the 
piston is at the beginning of its stroke. (This is more fully shown in 
Fig. 4, where the arrow A denotes the direction of the steam through such 
opening. ) The action of " lead " is threefold : First, it admits steam to 
the piston before it has arrived at the end of the stroke, and this steam 
acts as a cushion, enabling the piston to reverse its motion easily; second, 
it assists the admission of steam, tending to permit the steam passage to 
become supplied with steam at full steam-chest pressure by the time the 
piston reverses its motion; third, it assists the exhaust, which is of espe- 
cial importance to a valve like that shown in Fig. 1. 

The diagram A shows no early action, but the diagram B shows cut-off 
before the end of the stroke and release and compression at between 95 
and 100 per cent, of the stroke. 

With no steam lap nor lead, the steam is admitted full stroke and does 
not give up the energy which might be realized from its expansion. By 
adding lead, one step in the right direction is taken, but it is not insufficient 
for the reason that with a minimum of lead, with no steam lap, the steam 
on the exhaust side cannot escape quickly enough to prevent its exerting 
a back pressure on the piston. 

" Lap," as generally used, and unless otherwise specified, means steam 
lap, and " steam lap " means the amount the steam edges a a, Fig. 2, over- 
lap the steam edges d d when the valve is in the mid-position. The steam 
lap is provided mainly to cut off the suppl}^ of steam from the steam chest 
into the cylinder at some point earlier than the end of the stroke, and 
the point of the stroke where the supply is cut off is called the " point of 
cut-off." The determination of this point depends upon the speed of the 
engine. 

Another object of the steam lap is the obtainment of free exhaust, which 
is of great importance in a high-speed engine. Increased valve lap calls 
for increased travel, which also aids exhaust. 

The difference in valve travel, with and without lap, will be seen by 
comparison of the valve-travel circles in Figs. 1 and 2. In Fig. 1 it 
is shown that the valve travel equals twice the width of the port, while 



THE SLIDE VALVE EXPLAINED 5 

Fig. 2 shows that the valve travel is equivalent to twice the width of 
the port plus the lap. When the valve is in mid-position, as in Fig. 2, 
the steam edges a a are in positions corresponding to the center of travel 
a' a'. At this point the valve is lapped on the steam edges, and the ex- 
haust edges & h, not being lapped, are line and line with the exhaust edges 
c c of the cylinder ports. When the valve moves in one direction, so that 
one steam edge a of the valve becomes even with the steam edge d of 
the port, it will correspond with the point d' in the valve circle; while 
the other edge a has advanced to the point f on the valve seat, which cor- 
responds to the point f in the valve circle, and the edge & on this end 




FIG. 2. 



has advanced to the edge d of the steam port. The valve would then be 
in position to admit steam to one port and leave the opposite port wide 
open for exhaust. 

Where the edge a of the valve has advanced to the edge c of the cyl- 
inder port, the opposite edge a has advanced to the point e on the valve 
seat, corresponding to the point e' in the valve circle. The steam port 
on the one side is now wide open, and the exhaust port on the other side 
is still wide open. At this juncture the valve has reached the limit of its 
travel in one direction, and upon reversing its travel the first edge a of 
the valve reaches the edge d of the port and cuts off the steam at about 
three quarters of the piston travel. The valve continuing until the edge 
a meets the point a on the valve seat, the exhaust has again closed on one 
end and is about to open at the other end ; and so the action continues. 



VALVE SETTING 



Tracing the Action in Detail 



To get a more complete understanding of this, it will be well to follow 
the valve action, by means of Fig. 3 and succeeding illustrations, through 
one complete revolution of the crank of the engine. The lap represented 
is 25 per cent, of the travel, the two valve circles being so placed with 
reference to the valve as to clearly indicate the action of each end. In 
all the illustrations the position of the crank on the circle is shown at c, 




FIG. 3. 



and the position of the eccentric, in relation to the crank, at e. The 
graduated scale in several of the crank-end circles is for convenience in 
identifying the position of the crank in per cent, of stroke at any point 
of the valve movement. The point of intersection with the line B B oi 
the arc of a circle which would bisect the crank-end circle C shows the 
relative position of the piston in per cent, of its stroke. The valve circles 
are marked H and C to indicate the head and crank ends of the cylinder, 
respectively. The arrows denote the direction of movement, and the ports 
and edges are the same as in Figs. 1 and 2. 



THE SLIDE VALVE EXPLAINED 7 

Fig. 3 shows the valve about to open, with tlie position of the eccentric 
e, in relation to the position of the crank c, as shown, or when the angle 
of advance is just sufficient to overcome the lap. With the angular ad- 
vance no greater than that indicated, diagrams such as those shown beneath 
the circles are obtained, the principal features of which are cut-off when 
near 75 per cent, of the piston travel and release and compression at from 
90 to 95 per cent, of the stroke. It will be noted that while the exhaust 
(owing to greater valve travel than shown in Fig. 1) is full open at the 
same position of the crank, neither release nor compression sets in much 
earlier in the stroke. 

In Fig. 4 the same valve is given lead, while the crank still remains 
at the beginning of the stroke. This admits steam in the direction of 





L 




FIG. 4. 



the arrow A, the exhaust being in the direction of the arrow B at the 
same time. 

In Fig. 5 the head-end steam port is full open at the same time that 
the crank-end exhaust is still full open. The eccentric e is at the end 
of its travel and the crank c is relatively in the position shown. The 
piston would be at about 30 per cent, of its travel. 



8 



VALVE SETTING 



Fig. 6 shows the valve at the point of cut-off for the head end. The 
steam is cut off and the exhaust still remains open on the crank end. 
The piston has reached about 75 per cent, of its travel, with the crank 
and eccentric as shown. 

Fig. 7 shows the exhaust about to release on the head end, and just 
closed for compression on the crank end. The piston has reached nearly 
93 per cent, of stroke. 

Fig. 8 shows the cylinder port on the head end wide open for exhaust, 
and the crank end of the valve open for lead on the crank-end port, with 
the piston at the beginning of its return stroke. 






FIG. 5. 



Fig. 9 shows the valve having reached the extreme of its travel in 
the direction shown, leaving the head-end port wide open for exhaust and 
the crank-end port wide open for steam, the piston having advanced to 
about 25 per cent, of its return stroke. 

Fig. 10 shows the valve at the point of cut-off on the crank end, with 
the head-end port still open to the exhaust. The piston in this case will 
not have traveled quite as far as it did on the head-end cut-off. 

Fig. 11 shows the valve centered on its travel again, with the exhaust 



THE SLIDE VALVE EXPLAINED 9 

just closed on the lieacl end, and at the point of release on the crank end. 
The piston has reached about 90 per cent, of its return travel. 

How THE I>rDICATOR DIAGRAM IS MaDE 

Suppose an indicator were located at each end of the cylinder, with 
the pencil points in contact at the beginning of the valve action shown in 
these illustrations, for the purpose of making simultaneous records. Then 
referring back to Fig. 4, it will be found that the line of admission has 
been recorded on the head end and the line of release on the crank end. 





<- 




FIG. 6. 



Fig. 5 shows the admission line being recorded on the head end and the 
counter-pressure line on the crank end. Fig. 6 shows the admission line 
on the head end completed up to the point of cut-off, and the counter- 
pressure line on the crank end still extending. Fig. 7 shows that the 
expansion line on the head end has been developed to the point of release, 
and the counter-pressure line on the crank end has arrived at the point 
of compression, or exhaust closure. Fig. 8 shows that the release line on 
the head end has developed, and that compression and admission have 



10 



VALVE SETTING 



occurred on the crank end. Fig, 9 shows the start of the counter-pressure 
line on the head end, and the admission line on the crank end, also. Fig. 
10 shows the head-end counter-pressure line still extending and the crank- 
end admission line extended to the point of cut-off. Fig. 11 shows the 
completed action with the following approximate results: 



Cut-off, per cent, of stroke 

Release, per cent, of stroke 

Compression, per cent, of stroke 



Crank 
End 




Positive and Negative Exhaust Lap 

In adding sufficient steam lap to bring about good cut-off, the exhaust 
is apt to be released too early, and exhaust lap is provided to obviate such 




\J 





FIG. 7. 



defect. Exhaust lap is the amount the exhaust edges (& &^ Fig. 12) of 
the valve overlap the exhaust edges c c of the cylinder ports when the 
valve is in mid-position, as shown. In Fig. 12 the valve travel is equal 



THE SLIDE VALVE EXPLAINED 



11 



to twice the width of the port plus the steam and exhaust lap, with the 
center and extremes of travel as shown by the circle. 

Where valves require small steam lap or excessive travel, it is sometimes 
necessary to provide negative or exhaust clearance to free the exhaust. 
Negative lap or exhaust clearance is the amount of opening (Fig. 13) 
between the exhaust edges & & of the valve and the exhaust edges c c of 
the cylinder ports when the valve is in the mid-position of its travel. In 





^r 




FIG. 8. 



Fig. 13 the valve travel will equal twice the width of the port, plus the 
steam lap, as in Fig. 3. 

Other Important Considerations 

Eeferring to Fig. 14, linear advance of an eccentric is the linear dis- 
tance equaling the lap and lead measured on a like perpendicular to the 
90-degree radius H c, meeting the circumference of the circle of the eccen- 
tric revolution, as at B. The distance .1 B is the linear advance. 

Angular advance of an eccentric is the angle corresponding to a sine 
whose length is twice the lap in per cent, of travel. For example, the 
angle E c B, Fig. 14. 



12 



VALVE SETTING 



Example 

The steam lap is assumed to he 25 per cent, of the valve travel and 
there is no lead; what is the ang'ular advance? 

The valve travel in the illustration (Fig. 14) is proportional to the 
line J^ F. Twenty-five per cent, of this multiplied by two equals one half 
of the radius cF. By referring to a table of natural sines, it is seen 
that the angle corresponding to a sine equaling 0.50 is 30 degrees. In 
this case, then, 30 degrees is the angular advance. 





FIG. 9. 



In case there is lead, the lead angle must be added, as follows: Lap, 
26 per cent. ; lead, 2 per cent. ; total, 27 per cent. Then, 27X2 = 0.54. 
Eef erring again to the table, the angle of advance is found to be 32 degrees 
minus 41 minutes. 

The angle of admission is the angle the crank pin passes through (be- 
ginning at the end of the stroke) prior to cut-off. It is always 180 de- 
grees minus twice the angular advance, as, for example, the angle E cB, 
Fig. 14. In the above example, the angle of admission would be 180 



THE SLIDE VALVE EXPLAINED 



13 



degrees — (32 degrees -il minutes X 2) =114 degrees 38 minutes. It fol- 
lows that if there were no lap, there would be no angular advance, as 
shown in the valve circle in Fig. 1, and the angle of admission would be 
180 degrees, or full stroke. On the other hand, if the lap equaled 50 
per cent, of the valve travel, the sine of the angular advance becomes 1, 
and the angular advance is 90 degrees, which multiplied by two equals 
180 degrees, and there would be no angle of admission, as 180 — 180 = ; 
and steam would be cut off at the beginning of stroke, there being no 
lead. If lead were used, the angle of admission would be that due to the 



yfS^ — 


^ / 


^ 


r\ 


B 


B I 1 ) 


^ M 1 l/l 1 \l 1 hi 1 




1 nil 


II Ik 


n Mil Ml 








VJ ^ 


>^- 


y J 




, 


^ / 




-J 






FIG. 10. 



lead only. The above examples serve when the admission is greater than 
50 per cent, of the stroke. 

The period of admission, when less than 50 per cent, of the stroke, is 
equal to one half the versed sine of the angle of admission, as A B, Fig. 
15. If the cut-off occurs beyond the half stroke, the period of admission 
equals one half the stroke plus one half the sine of the angle exceeding 
90 degrees, as H C K, Fig. 16. 



14 



VALVE SETTING 



Example 

The lap equals 40 per cent, of the valve travel. This equals 40 X 3 = 
0.80 radius. The angular advance therefore is the angle corresponding to 
a sine 0.80. The angle is 53 degrees 15 minutes; the angle of admission, 
therefore, is 180 degrees — (53 degrees 15 minutes X 3) = 73 degrees 30 
minutes, which is less than one-quarter revolution or one-half stroke. The 
period of admission is actually one half the versed sine of 73 degrees 30 





-> 




FIG. 11. 



minutes, which is equal to 47.9 per cent, of stroke. Eefer again to Fig. 
15, in which K C A is the angle of admission, either angle LCD, K C L, 
or A C P being the angular advance, and R P the linear advance equaling 
the lap. 

If the lap were 30 per cent, of the valve travel, the angular advance 
would be 30 X 2 := 0.60 = 37 degrees, and the angle of admission would 
be 180 — (37 X 2) = 106 degrees, and the period of admission would be 
one half the versed sine of 90 degrees plus one half the sine of 16 degrees, 
or 63 per cent, of the stroke. 



THE SLIDE VALVE EXPLAINED 



15 



The Exhaust 

Assuming no exhaust lap, the opening and closing will occur when a 
portion of the stroke equaling one half the versed sine of the angular 
advance is still incompleted. That is to say, the angle of compression and 
the angle of prelease are equal to each other and equal also to the angle 
of advance. It follows that if the lap is. 50 per cent, of valve travel, the 
angular advance would be 90 degrees, with the exhaust opening and closing 
at 50 per cent, of the stroke. On the other hand, if there were no steam 
lap nor lead, there would be no angular advance, and the exhaust would 
open and close at the end of the stroke. 

Angularity of the Connecting Rod 

The angularity of the connecting rod with the center line lengthens 
the admission on the head end and shortens it on the crank end, as has 




FIG. 12. 



been shown in Figs. 4 to 11, inclusive, and summed up at the end and 
further explained here. The amount the cut-ojff is retarded during the 
out stroke and hastened during the in stroke depends upon the ratio of the 
length of the rod to the crank travel. In the examples already given, 
the ratio of rod to travel was 3 to 1. The point of cut-off also depends on 
the position of the crank at the time cut-oif occurs. The amount 
the admission is lengthened on the out stroke (or the down stroke of a 



16 



VALVE SETTING 



vertical engine), and shortened on the in stroke (or the np stroke of 
a vertical engine), by the angularity of the connecting rod, is the versed 
sine of the angle of the rod multiplied hy the ratio of the crank divided 
hy two. 

The angle of the rod may be found by dividing the sine of the crank 




FIG. 13. 



angle by the ratio of the rod to the crank. The quotient is the sine of 
the ano;le of the rod. 



Example 

Assume the crank angle to be 60 degrees. The sine of 60 degrees = 
0.866. This sine divided by the ratio of the rod to the crank (say 6) = 
0.144, which is the sine of the connecting rod, and the angle is 8 degrees, 
nearly. Again, the reversed sine of 8 degrees = 0.00973. This multiplied 
by 6 -f- 3 =: 2 per cent., nearly, which is the amount the admission is length- 
ened on the out stroke and shortened 
on the in stroke. The exhaust is af- 
fected in the same way, only as the 
crank angles are smaller at exhaust, 
the full effect is not so great, as is 
shown by table of results of valve 
movements. The nearer to the one- 
half stroke of the crank the cut-off or 
release and compression occur, the 
greater the amount of difference in per 
cent, on the two strokes, and the 
nearer the beginning and end of the 
stroke the less the percentage. 

It has been shown that the pre- 
exhaust angle equals the angular ad- 
vance (when no inside lap is used). Therefore, the sine of the angle of 
the connecting rod at exhaust is the sine of that angular advance of the 
eccentric which equals the lap and lead. 




THE SLIDE VALVE EXPLAINED 



17 



Example 

Assume the lap to be 30 per cent, of the valve travel or 0.60 radius. 
The lap being the sine of the angular advance, it will be 6 times the sine 
of the connnecting-rod angle, 0.60 -^ 6 = 0.10. which is the sine of the 
latter, and the angle is 5 degrees 45 minutes. 

The reversed sine of 5 degrees 45 minutes is 0.005. The point of ex- 
haust, therefore, would be delayed 0.005 X (6 f- 2) = 0.015 per cent, of 




FIG. 15. 



the out or down stroke, and hastened the same per cent, on the in or up 
stroke. 

To correct for the angularity of the rod, it is customary to give less 
lead at the head end than at the crank end. It may be done also in the 
arrangement of the valve gear where rockers are used, placing the rocker 
arms in such position as to give the valve more rapid opening and closing 
movements on the head end than on the crank end. Professor Sweet pro- 
vides for equal cut-off in this manner. Similar construction has been used 
by Mr. Williams and other designers. 

Providing greater lead at the crank end than at the head end not only 
serves to correct the admission but the exhaust also, only it is not sufficient 




FIG. 16. 



for the latter. To equalize the compression, therefore, it is customary to 
use less inside exhaust lap at the head end than at the crank end. Or, the 
crank end may be made line and line if the cylinder clearance is small, 
and the lap at the head end is cut away so as to give negative lap at that end 



18 VALVE SETTING 

when the valve is centrally located. About from 1 to 3 per cent, is gen- 
erally sufficient;, the object being to reduce the terminal compression at 
both ends to about three fourths of initial compression. 

When the rods are very short, as in marine engines (sometimes of as 
low as 1.7 ratio), it is quite, or almost, impossible to equalize the cut-off 
with a single valve, and also very little loss occurs from a moderate degree 
of inequality. 

Method of Laying Out Valve Motion 

In Figs. 15 and 16 is shown a method of laying out the valve motion 
used by E. F. Williams, designing engineer^ which recommends itself on 
account of its simplicity. The lines M D are drawn to represent the 
center line of the engine indefinite. From C as a center, draw the circum- 
ference P A K H L D, representing both the travel of the crank pin and 
that of the eccentric. Draw the vertical downward from the center line 
a distance equaling the lap and lead, meeting the travel circle at P. Draw 
the diameter P L and erect the perpendicular L F. The distance A F is 
the travel of piston prior to release, and the distance F D is the pre-release. 
Make the angle K C D equal to twice the angular advance LCD; the 
remaining angle K C A (shaded) is the angle of admission, and the period 
of admission is A B, the connecting rod being considered infinite. 

To correct for the angle of the rod, draw the line M K for the steam 
admission, and the line N L for the exhaust, making the ratio of MK 
to K C and N L to L C equal to the ratio of the connecting rod to the 
crank. From the points M and N scribe the arcs K E and L 0. 

The point E will be the point of cut-off and G the point of release, 
corrected for the angles of the connecting rod. 



II 



A STUDY OF THE D SLIDE VALVE* 

It will now be in order to take up more in detail the effects of chang- 
ing the valve setting, and the methods of using the diagram for de- 
signing and proportioning valves for new engines or for remodeling 
valves in engines already in operation. It will be seen in Fig. 17 that 
if the outside lap is increased an amount corresponding to N — M on the 
scale of the diagram, admission will take place later, at the crank posi- 
tion — A', where the lead will be reduced to I — G, and cut-off will take 
place earlier at — C. On the other hand, the contrary effects are seen 
where the outside lap is reduced, and if the inside lap be increased an 
amount equal to L — S release will take place later, or at the crank posi- 




riG. 17. 




tion — B', and compression will take place earlier, at — Z)', the effect 
being exactly opposite for a decrease of the inside lap. 

In Fig, 18 is shown the effect of altering the angular advance of the 
eccentric. It will be seen that if the angle of advance is increased, as 
at a', all the events of the valve occur earlier, since the crank revolves 
in the direction indicated by the arrow, and the new position of admission 
— A' is ahead of — A, the old position. This is true also of the other 
valve movements, — E' being ahead of — E, and — C ahead of — C. 

* Contributed to Power by E. S. Hawkins. 

19 



20 



VALVE SETTING 



A third alteration that may be made in the valve gear is a change of 
eccentricity, by altering the eccentric radius, when making a design, or 
by using a new eccentric of radius different from that of the older one, 
where an engine is being rebuilt. The effect of a change in eccentricity 
is shown in Fig. 19, in which it will be noted that when the eccentricity 
is increased, the valve travel is increased, and admission takes place ear- 
lier (at — A), the lead being in- 
creased an amount equal to / — I', 
while cut-off takes place later (at 
— C") ; — B' in the figure comes 
ahead of — B, showing that release 
is earlier the greater the eccentricity 
and, since — D' comes after — D, 
it is plain that compression is later. 
Since the upper valve circle cuts the 
arc drawn from as the center, with 
a radius equal to the outside lap plus 
the width of the steam port, in the 
points W and H', the admission port 
will be open wide, while the crank moves from — W to — H'. On the 
lower valve circle it is shown that the exhaust port opens sooner (at 1^) 
and remains open longer (at iJ). It is plain, of course, that decrease of 
the eccentricity will have a contrary effect. 

Table Showing in Condensed Form Effect of Changes in Lap, Travel of Valve, 
OR Angular Advance of Eccentric 




FIG. 19. 



Admission. 



Expansion. 



Exhaust . 



Compression. . . . 



Increasing 
Outside Lap 



Is later 
Ceases sooner 
Is earlier 
Continues longer 

Unchanged 



Begins at 

same point 



Increasing 
Inside Lap 



Not changed 

Beginning 

unchanged 
Continues longer 

Occurs later 

Ceases sooner 

Begins sooner 

Continues longer 



Increasing 
Travel 



Begins earlier 
Continues longer 
Begins later 
Ceases sooner 
Begins earlier 
Ceases later 
Begins later 
Ceases sooner 



Increasing 
Angular 
Advance 



Begins earlier 
Same period 
Begins earlier 
Same period 
Begins earlier 
Same period 
Begins earlier 
Same period 



The accompanying table shows in condensed form the effect of changes 
in the lap, travel of the valve, or the angular advance of the eccentric. 



A STUDY OF THE D SLIDE VALVE 21 

From what has been said, it will be seen that in all problems using 
the valve diagram, there are, in addition to the four valve movements of 
admission, cut-off, release, and compression, the other variables of valve 
travel, angle of lead, outside lap, and inside lap. In every problem, some 
of these items are given and the others must be found and, in designing 
an engine, the conditions under which it is to be used determine certain 
of the elements which are then considered fixed, and are used in com- 
putations to determine the other variables. In general, the work of any 
case will fall under one of five problems, each of which will be here 
explained. 

Problem I. Given the travel of valve and points of admission, 
cut-off, and release. 

In Fig. 20, let C — Fg equal the given travel of the valve, and on this 
line as a diameter construct a circle, marking on it the points K, P, and P, 
for the given, points of admission, cut-off, and release. Through K and P 
draw the line K — P, and through draw the line Cg — C^ perpendicular 
to the line K — P. From P^ draw the line Pg — ^i parallel to K — P, 
and intersecting the line C^ — C^ at the point M^, the distance of which 
from the center is the exhaust lap of the valve, while the similar dis- 
tance of the point M on the line K — P from the center is the lap of the 
steam valve. By drawing in the valve circles and the lap circles through 
the points M and M^, the leads N — Q and N^ — Q^ are determined. 

Problem II. Given the travel of valve, steam lap, steam lead, and 
any point in the exhaust diagram. 

In this case the crank circle is constructed as before, and the distance 
— N laid off equal to the lap plus the lead. At the point N the per- 
pendicular N — Cg is erected, cutting the crank circle in the point Og. 
It is plain then that the angle Cg — — R is the angle of advance and 
the diagram is completed by drawing the diameter Cg — — C^, and fol- 
lowing out the construction by drawing in the valve and lap circles. 

Problem III. Given the travel of valve, cut-off, steam lead, and ex- 
haust lap, ' 

First construct the valve circle as before and mark on it the point 
P corresponding to the point of cut-off. With the point C as a center 
and a radius equal to the lead (which is given), draw in a circle, as 
shown in the figure, and from the point P draw a line passing tangent 
to this circle on the under side. This line will cut the large circle at 
the point K, which is the point of admission. By drawing a diameter 
through the point perpendicular to the line K — P the angle of advance 
is determined, after which the rest of the construction can readily be 
carried out. 

Problem IV. Given the steam lap, steam lead, and the point of 
cut-off. 



22 



VALVE SETTING 



In Fig. 20, let the angle C — — P be that corresponding to the point 
of cut-off and draw in the lap circle Q M L, laying off at the same time 
the distance Q — N equal to the lead. Connect the points N and and 
the points and L by straight lines, and erect a perpendicular to each 
of these lines at its middle point. The point Oi at which these two 
perpendiculars intersect will be the center of the steam-valve circle and 
the radius will be the distance from it to the point 0, or either of the 
points N and L. The diameter of this circle is, of course, equal to one 
half the travel of the valve, so that the crank circle may readily be 
constructed, and the angle Cg — — R between the diameter of the valve 
circle and the perpendicular erected from the point will be the angle 
of advance. It is, then, an easy matter to carry out the construction and 





FIG. 20. 



FIG. 21. 



finish the diagram by drawing in the other valve circle and the two lap 
circles, and laying off on the crank circle the points corresponding to the 
other valve movements. 

Problem V. Given the cut-off, release, compression, and width of 
port. 

It is assumed that the width of the port is equal to the maximum 
opening of the exhaust port, and to construct the diagram it will first 
be necessary to find the travel of the valve, which is done, as shown in 
Fig. 21, by drawing a circle of indefinite radius and marking on it points 
of cut-off, release, and compression. This can readily be done, since these 
points, if given in terms of the stroke, as explained in Chapter III, 
may be found in terms of the angle turned through by the crank. Join 
the points of release and compression by the line A — B and through 
draw a diameter perpendicular to this line. It is then plain that the 
ratio of valve travel to the given width of port is equal to the ratio of 
W — Y to X — Y ; and from this the travel of the valve is obtained and 
used as the diameter of a new crank circle, which, when drawn, has the 



A STUDY OF THE D SLIDE VALVE 23 

points of cut-off, release, and compression laid down and the diagram 
drawn as per the problem already given. 

Sometimes the point of release is given instead of the width of port, 
and in this case the travel of valve is found by drawing through the 
point P a line parallel to A — B and from the point dropping a per- 
pendicular to this line at E. The line C — E is then proportional to the 
lead, so that we have the ratio travel of valve to given lead equals 17 — Y 
to C — E, from which the travel of valve is found as before. In these 
cases the distance W — Y is multiplied by the width of port or by the 
given lead, as the case may be, and the product divided by the distance 
X — Y or C — E, to find the travel of the valve in actual inches. This 
dimension must, of course, be altered to, correspond with the scale selected 
for drawing the diagram. 

As illustrations of the practical working of the diagram a number of 
examples with solutions will be given. 

1. Travel of the valve is 6 ins. and cut-off occurs when the crank has 
completed 105 degrees of its path. Admission of steam begins when the 
crank is within 7.5 degrees of the beginning of its stroke, and exhaust 
closes when it is 60 degrees from the end of its stroke. Construct the 
Zeuner's valve diagram and tind the steam lap, steam lead, exhaust lap, 
exhaust lead, and the angle of advance. 

As the first step, select some scale to which the diagram is to be drawn 
and, as in this case the travel is 6 ins., one half this length may con- 
veniently be used for the diameter of the crank circle, which is drawn 
as shown in Fig. 22. On this circle, the given points of admission, cut-off, 
and compression are laid down at K, P, and P^, respectively, making the 
arcs C — K, C — P, and C — P4 equal, respectively, to the given angles of 
7.5, 105, and 60 degrees. A line is then dra^vn connecting the points 
K and P, and, through the center of the circle, a diameter is drawn 
perpendicular to this line, intersecting the crank circle in the points A 
and B and the line K — P at M. By measurement, the angle A — — A' 
is found to be 42.5 degrees and this is the angle of advance required to 
be found. With the lines — A and — B as diameters, valve circles are 
dra^-n in and, with as the center and — M as the radius, the steam- 
lap circle is drawn, — M being one half the steam lap, which by measure- 
ment is found to be ^ of an inch. The distance N — Q between the 
intersections of the valve and the lap circles with the line — C is found 
to be -^Q of an inch, and this is one half the steam lead. 

To find the exhaust lap and lead, draw from the point P^ a line per- 
pendicular to the diameter A — B, and intersecting this diameter at the 
point M', the distance of which from the center of the crank circle 
is the exhaust lap, so that the circle described with as its center and 
the distance — M' as a radius is the exhaust-lap circle and the distance 



24 



VALVE SETTING 



Q' — TV' betM^een its intersection with the line — Pg and that of the 
exhaust- valve circle is found to be yV of ^"^ inch, which is one half the 
exhaust lead of the valve; — W is -^ in., so that the exhaust lap is \ of 
an inch. 

2. A valve has a travel of 5 ins., a steam lap of 1 in., an exhaust lap 
of \ in., and a steam lead of \ in. It is required to find the angle of 
advance and the point of cut-off. The stroke of the engine is 4 ft. and 
the connecting rod is considered to be of infinite length, so that its 




FIG. 22. 



angularity may be disregarded. It is also required to determine what 
should be the steam lap of the valve if steam is to be cut off at half 
stroke; what should be the angle of advance to make the engine cut off at 
half stroke, and how this change would afEect the other functions of 
the valve. 

Here the travel of the valve is 5 ins., and one half of this may be 
taken as the diameter of the crank circle, which is shown in Fig. 33 
with the two diameters C — Pg and C — D at right angles. — M — 
as the center and the radius — M equal to one half of the given steam 
lap of 1 in,, the steam-lap circle Q M L is drawn in, and with a radius 
of ^ of an inch the lap circle for the exhaust valve is also drawn. Prom 
the point Q, where the steam-lap circle intersects the horizontal diameter 
G — Pg, the distance Q — N, equal to ^ of an inch, or one half the given 
steam lead, is laid off and, from the point N, a perpendicular is erected 



A STUDY OF THE D SLIDE VALVE 



25 



on the diameter C — Pg, intersecting the crank circle at the point A, from 
which the diameter A — — B is drawn. 

The angle A — — C is the angle of advance and by measurement is 
found to be 37 degrees. Since the connecting-rod length is considered 
infinite, the distance of the piston from the end of its stroke at cut-off 
will be equal to the distance N' — P^ from the foot of the perpendicular 
dropped on the diameter C — Pg from the point of cut-off P. By measure- 
ment this distance is found to be f of an inch, and since the scale of 
the diagram is 2^ ins. equal to the stroke of 4 ft., the distance of f of 
an inch will be exactly one-fourth stroke, so that this is the point of 
cut-off. This point is found on the diagram by drawing the line K — P 




through the intersection of the steam-lap circle with the diameter A — B 
at the point M, making the line K — P perpendicular to A — B. In this 
way, also, the admission point K is found. 

To find the amount of lap that would be required to make the cut-off 
come at half stroke, assume the cut-off to be at this point, or at the line 
— C in the figure, and from C draw a line to the point of admission 
at K; — A' is then drawn perpendicular to K — C", and the distance 
— M^, which by measurement is found to be f of an inch, is one half 
the steam lap that would be required to bring cut-off at half stroke. With 
this condition, the angle of advance will be A' — — C", which by measure- 
ment is found to be 51 degrees. This greater angle of advance would 
make the other movements of the valve come earlier in the stroke. 

3. A valve such as shown in Fig. 24 is to have a travel just sufficient 




26 VALVE SETTING 

to open the port wide for exhaust, when the exhaust is a maximum, and 
with a connecting rod considered of infinite length it is to cut off at 
three fourths of the stroke. The exhaust port is to begin opening when the 
piston is at one eighth of its stroke from the end and admission occurs 
at one sixteenth of the stroke. It is required to find the steam and ex- 
haust laps, the travel of the valve, the angle of advance of the eccentric, 
and the position of the piston at exhaust closure. 

To solve this problem draw a circle, as in Fig. 25, making the diam- 
eter of any convenient length, which in this case is taken as 3 ins., and 
draw also the diameters C — Pg and A' — B' at right angles. On the 
diameter C — Pg the distance C — Q is 2^ ins., or three quarters of the diam- 
eter. At this point erect a perpendicular to the diameter, intersecting 

the circle at the point P, which will 
be the point of cut-off. In a similar 
way the point Q' is located, so that 
its distance from the point P^ is f 
of an inch, or one-eighth stroke from 
the outer dead center Pg, and the 
piQ 24. perpendicular erected from this 

point Q' intersecting the circle at 
the point P' locates the point of release. In a similar way the point N is 
found one eighth of the stroke, or ^ of an inch from the point C and 
the perpendicular dropped to the circle, intersecting it at K, the point 
of admission. 

By connecting the points K and P with line K — M — P and drawing 
a diameter through the center perpendicular to this line, the angle of 
advance A — — A' is located and this is found to be 44 degrees. To 
find the point of exhaust closure or compression, draw from P' a line 
perpendicular to the diameter A — B and intersecting the crank circle at 
the point K', which will be the point of compression. By drawing from 
this point a line perpendicular to the diameter C — Pg and intersecting 
it at the point iV', which is -J in. from C, it is seen that compression takes 
place when the piston is one sixth of its return stroke from the inner 
dead center C. Fig. 24 shows that the width of the port is 2 ins., and 
this, therefore, is the maximum opening to exhaust, so that, according to 
the conditions given in Problem V, the travel of the valve -f- given width 
of port = A—B -f- M'—B, Fig. 25. The width of the port is 2 ins., as 
just stated, so that the travel of the valve is equal to 2 X l-j -^ M' — B, 
which is found by measurement to be 1-|| ins. This gives the valve travel 
as 2.13 ins. (4.26 ins. actual, as the diagram is half scale), so that all 
linear dimensions taken from the diagram as drawn in Fig. 25 must be 
reduced in the ratio of 2.13 to 3. Eeducing the distance — M, which 
measures | of an inch by this ratio, we find that the actual steam lap is 



A STUDY OF THE D SLIDE VALVE 



27 



0.533 in.; and the exhaust lap — M' , reduced in a similar way from its 
actual measurement of -j\ of an inch, gives the actual amount of lap as 
0.133 in. 

■i. In a given engine, cut-off is to take place when the crank is 45 
degrees from the end of its stroke, release being at 15 degrees from the 
end of the stroke and admission at 7.5 degrees from the beginning of 
the stroke. The maximum exhaust port opening is 2.5 ins. and it is 




required to find the travel of the valve, the steam and exhaust laps, the 
crank angle when compression begins and the exhaust lead. 

Again making the diagram one half full size, draw the two lines 
C — Pg and A' — B' perpendicular to each other, as in Fig. 26, and from 
their point of intersection draw the line — K, making an angle of 
7.5 degrees with — C, also the line — P, making an angle of 45 degrees 
with — Pg and the line — Pi, making an angle of 15 degrees with 
— Pg. We then lay otf from the point on the lines — K and — P 
equal distances, 1-| ins., as shown in the figure, and connect the points 
K and P thus found. Through the point the line A — B is drawn 
perpendicular to the line K — P and from the point P', which is also 
1^ ins. distant from 0, the line P' — K.2, is drawn parallel to K — P, so 
that it is also perpendicular to the line A — B. From its point 
of intersection M' with the line A — B, lay off the distance 1^ ins. to 



28 



VALVE SETTING 



the point B. With as the center, and with — B as a radius, draw 
the circle as shown. This will be the crank circle and its diameter 
C — P3 the travel of the valve, which by measurement is found to be 3 
ins. (6 ins, actual) while the distance — M, or the steam lap, is by 
measurement found to be ^ in. (1 in. actual) and the exhaust lap — M', 
^ of an inch (^ in. actual), the crank angle at compression C — — K^, 
36 degrees, and the steam lead N — Q, | in. on the diagram or 0.5 in. 




actual, while the exhaust lead N' — Q' is ^ of an inch on the diagram 
or -ff actual. 

It so happens in this case that the distance selected to lay off on the 
lines — P and — K was 1^ ins., or one half the valve travel, but this 
is not necessarily the case, as the solution will be unaffected no matter 
what distance is laid off. Thus, for instance, if we should lay off 1 in. 
on — P and — K to the points K' and P' and join these points by a 
line as shoM^n, we would still be able to draw the line A — B perpendicular 
to the dotted line so that its angle with the vertical A' — B' would be the 
same as at first. All of the linear dimensions of the diagram are deter- 
mined by the maximum opening to exhaust, 2^ ins., which is laid off 
from the point M' to B, as already described, for determining the radius 
for the crank circle. 



Ill 

A STUDY OF THE ZEUNEE SLIDE-VALVE DIAGRAM* 

Probably every engineer at some time or other has had a nice job of 
valve setting on his hands. In fact, it is quite common to hear an en- 
gineer begin a conversation with some such remark as this: "Well, the 
worst job I ever had was to set the valves on an old high-speed engine 
with a riding cut-oif valve/' In another case it may be an experience 
in setting the valves of a double-eccentric Corliss, or, perhaps, in still a 
third case it was a tandem or cross compound engine. Wherever one 
goes, he is sure to meet an engineer who is on the lookout for a patent- 
medicine cure-all that will be a sure preventer of the troubles met in set- 
ting valves. Perhaps this may not appear unusual when one considers the 
fact that on the proper or improper setting of the valves may depend 
the balance of profit or loss when it comes to the final reckoning at the 
end of the year. 

For those who have mastered the principles of valve operation, the 
work of setting the valves is simple, but to a large nmnber of engineers 
the functions of the valve seem to be hidden behind the valve-chest cover. 
Even with the cover removed and the valve parts in plain sight, it is not 
always clear as to just what changes are necessary to obtain a desired 
result. In some cases it is possible to tell at a glance where the trouble 
lies, but in others one must make a careful study of the case, considering 
the movements of the valve in their relation to the engine piston. 

The making of this analysis is not an easy matter for those unfamiliar 
with mathematical problems, and, although many men can by a few figures 
or rule-of-thumb methods determine what the valve conditions should be, 
there are others for whom the task is not so simple. To these men, ob- 
jects, lines, and dimensions that are visible to the eye make the subject 
much clearer than could be done by the mazes of mathematics only suit- 
able for exploration by the logically trained analyst. It is, therefore, with 
a view to meeting the needs of the practical man, to whom the chalk 
sketch tells everything, that this article is written. 

Several methods of graphically solving slide-valve problems have been 
worked out, but Zeuner's diagram is, perhaps, the most useful and simple 

* Contributed to Power by E. S. Hawkins. 
29 



30 VALVE SETTING 

of all and will, therefore, be considered in detail. By means of the dia- 
gram, the effect on the steam supply of changes in the dimensions of the 
valve, or in the adjustment of the eccentric, etc., are made actually visible. 

It is assumed that the length of the eccentric rod is infinite or, in 
other words, that it moves in a line parallel to the piston rod. This 
assumption can safely be made, since the angle due to the eccentric radius 
is so small as to have no appreciable effect on the results. Given the 
points at which admission, cut-off, etc., take place, the diagram shows the 
relative crank position. Conversely, the position of the valve correspond- 
ing to a given crank position may be found readily. By the use of the 
valve diagram in connection with the indicator, it is possible to diagnose 
a case of valve trouble so as to know the dimensions of the valve and the 
way in which it performs its functions as accurately and certainly as if 
it were seen operating within a transparent chest. 

For the sake of clearness, let it be supposed first, that the valve has 
no lap and that the line — Q, as in Fig. 27, represents the eccentric 
radius, so that the eccentric travels in the large circle as indicated by 
the arrow. When it is at Q, the valve is closed, but as it moves around 
the circle the valve gradually opens until, when the eccentric is at the 
point H, the amount of opening is represented, to the scale of the dia- 
gram, by the distance — G. It will be noted here that the crank posi- 
tions are not shown, but for any given position of the eccentric in its 
circle, the corresponding position of the crank will be behind the eccentric 
position by 90 degrees plus the angle of advance. 

Since it is desirable to avoid the necessity of dropping perpendiculars 
to the line of valve travel, such as H — G in Fig. 27, it becomes necessary 
to construct a line each point of which is distant from the center by 
an amount equal to the valve travel corresponding to the eccentric position 
indicated by a line passing from through the given point. To do this, 
take the point as a center and, with — G as a radius, draw the arc G — L 
until it intersects the line — H. Then at the position H' of the eccen- 
tric, drop the perpendicular H' — G' to the line X — — Y and, with — G' 
as a radius, draw another arc intersecting the line — H'. By continu- 
ing this process, a number may be found each of which marks off on the 
line of eccentric position a distance from the point equal to the valve 
travel for the given position of the eccentric. Upon joining the points, 
such as L and L' , a closed curve is formed known as the valve circle. 

To prove that the curve is a circle, take the triangles — L — Y — 
and 0—G—H—O, as in Fig. 27, in which 0—Y equals 0—H and 0—G 
equals — L, while the angle L — — Y is common to both triangles. 
Since the two triangles have two sides and an included angle equal the 
one to the other, they can be placed in coincidence and are, therefore, 
equal the one to the other, so that the line H — G equals the line L — Y. 



A STUDY OF THE ZEUNER SLIDE-VALVE DIAGRAM 



31 



and the angle — L — Y, being the same as angle (J — (J — //, is a right 
angle. The right angle — L — Y being inscribed in the closed curve 
and on its diameter — Y, gives proof that the curve is a circle. 

Perhaps it may be thought' that the proof of the valve circle is long 
and unnecessar}^, but it is important to establish this fact since, after 
having done so, the circle can be drawn in on the eccentric radius 
as a diameter without plotting the points as at L. Thus the diagram 
is simplified and the work shortened. By reasoning similar to what 
has been given, the valve circle for the right-hand end of the valve 
can be drawn in at the left of the figure, as in Fig. 27 ; and, since the 
valve is supposed to have no laps, the two valve circles will be identical, 





that at the right of the figure representing the opening of the valve for 
the admission of steam at the left while, at the same time, the circle at 
the left of the figure represents the opening of the valve at the right 
hand for the escape of the exhaust steam. On the reverse stroke of the 
piston, what was before the circle for steam admission is that for exhaust 
and vice versa. Thus in Fig. 27, for the eccentric position J, the valve 
will be open for the admission of steam at the right-hand end by the 
distance — K. i 

In practice, it is not possible to have a valve with no lap, because if 
such a valve were constructed it could not be closed tight enough to pre- 
vent the escape of steam past the edge of the port; nor could the periods 
of admission and exhaust be regulated to secure the highest economy. 
Having, therefore, drawn in the valve circle in Fig. 28 by the process 
already described, it will be necessary to take account of the lap on the 
two sides of the valve, by drawing in the arcs C — D and A — B with 
centers at the point 0. The distance — C represents, to the scale taken, 
the amount of the steam or outside lap of the valve, while the distance 



32 VALVE SETTING 

— A represents the inside or exhaust lap. When, therefore, the eccen- 
tric is at the position W, Fig. 28, the amount the valve has opened at 
the left for the admission of steam is represented by the distance G — H, 
or the sector — H less the length of the steam lap — G by which 
amount it is necessary for the valve to travel before the port opens. Simi- 
larly, the distance I — J at the left of the diagram is the amount by which 
the valve is open for the exhaust of steam on the right-hand end for the 
same position W of the eccentric. 

Usually it is most convenient to refer all valve motions to the posi- 
tion of the crank, since it is easier to determine this position than that 
of the eccentric and, for this reason, it is now necessary to translate the 
eccentric positions, discussed in Figs. 27 and 28, to the corresponding 
crank positions. This is done in Fig. 29 by moving the diameter of the 
valve circles backward by an amount equal to 90 degrees plus the angle 
of advance. 

Suppose that the crank is on the inner dead center, as at C in Fig. 
29, the corresponding position of the eccentric is at P so that the angle 
P — — B is the angle of advance. This being the case, the distance 
— A represents the amount of valve travel from the mid position at 
the beginning of the stroke. As the crank revolves to the positions C^, 
C2, E^, etc., the eccentric moves through equal angles to the correspond- 
ing positions P^, P2, Ps, etc., until, at this latter point, it has had its 
maximum effect on the motion of the valve which has now reached the full 
limit of travel to the right. At this time, the crank is evidently at the point 
£'3 so that the angle R — — E^ equals the angle P — — R, or the angle of 
advance. The distances — A, — A^, — A^, and — Fg represent the 
travel of the valve from its mid position for the various crank positions 
Cj, Ci, C2, and E^. By sweeping circles from the points A, A-^, A,, etc., 
to the corresponding points E, E^, Eo, etc., with as a center and con- 
necting £'3 with any one of the points, such as E-^^, we ha'se a second 
method of proving the fact that the valve curve is a circle, for, as can 
readily be seen in the figure, the triangle — E^ — E^ is equal to the tri- 
angle — A^ — P^. 

As may be inferred from what has already been said, the amount 
that the valve overlaps the edge of the port when in the mid position is 
called the " lap," the part on the outside of the valve being known as 
the steam or outside lap while that on the inside is the exhaust lap. Be- 
fore the steam port can open, the valve must travel a distance equal to 
the amount of the lap and, after it has opened, the amount of opening 
is always equal to the amount of travel less the amount of lap. This 
fact has been shown diagrammatically in Fig. 28 and is also shown in 
Fig. 30, in which it will be seen that for the position K the opening of 
the port is zero. This point, therefore, represents the crank position at 



A STUDY OF THE ZEUxNER SLIDE-VALVE DIAGRAM 



33 



the instant the valve is ready to open or, in other words, the point of 
admission. It is evident from the diagram that at the point P the open- 
ing of the valve is again zero, so that this point is the position of the 
crank when the valve closes and cuts off the steam supply. 

When the crank is on the dead center, as at C in Fig. 30, the valve 
is open by the amount of lead, which is represented in the diagram by the 
distance N — Q on the line of dead centers. In a similar way, the amount 
that the valve is open to exhaust at the end of the stroke is knoA\Ti as 
the exhaust lead. 

It is now necessary to show the proof of some of the more important 
properties of the diagram as sho-vAm in Fig. 30. By examining the figure 
it will be seen that a perpendicular let fall from the point C^, where the 





FIG. 29. 



FIG. 30. 



valve-circle diameter intersects the crank circle, cuts the line of dead cen- 
ters at a point N distant from the center by an amount equal to the 
lap plus the lead of the valve. To prove that the line joining the points 
of admission and cut-off is tangent to the steam-lap circle, take the tri- 
angles C3 — — L and P — — M, of which the sides — P and — M 
are equal respectively to the sides — C3 and — L, and the angle 
C3 — — P is common to both of the triangles. Hence they are equal and 
the angle — M — P equals the angle — L — C3, which is a right angle, 
thus proving that the line P — M — K is tangent to the circular arc 
Q — M — L. From this proposition it follows that if a circle be drawn 
with the point C as the center and a radius equal to the lead, this circle 
will be tangent to the line K — P, which joins the points of admission and 
cut-off. As a proof, the line C — X is dra^Ti from C parallel to K — P, 
and therefore perpendicular to Cg — 0, so that the lines C — and C3 — 
are equal, as are also the angles — C — X and — C3 — N. Since the 
angle C — — C3 is common to both triangles, they are equal and X — 
= N—0, while X—M = N—Q = the lead. Lines C—X and M—R are 



34 VALVE SETTING 

parallel by construction, so that C — R = X — M =: the lead, and C — R — M 
is a right angle with the circle tangent to the line K — P. 

Another property that is useful in constructing the exhaust part of 
the diagram when the lap circle is so small that it does not give a sharp 
intersection with the valve circle, is the fact that if — F be drawn per- 
pendicular to — Cg, and a perpendicular be let fall from the point F 
on the admission line, it will be equal in length to the radius of the 
steam-lap circle. The truth of this proposition is readily seen from the 
fact that the triangles F — '0 — Y and — K — M are equal, because they 
have equal hypotenuses and are right-angled triangles with the angles 
F — — Y and M — K — equal. Lines F — I' and — M being similar 
sides of equal triangles are themselves equal. 

To construct the part of the diagram corresponding to the exhaust side 
of the valve, the reasoning is the same as that just given for the steam 
side, the piston being, however, on the return stroke from F^ to C, in 
Fig. 29, so that the valve circle comes in the lower half of the figure. 
The angle of advance and travel of the valve are the same as for the 
steam side of the diagram, but the lap is somewhat less, since economical 
performance requires as small a lap as possible, and the lower steam pres- 
sures usually prevailing on this side of the valve make it possible to have 
a tight seating valve without a great amount of lap. The exhaust lead 
and the points of release and compression correspond respectively to the 
steam lead and the points of admission and cut-off, and are obtained on 
the exhaust-valve circle in the same manner as the corresponding points of 
the steam-valve circle. 

Fig. 31 shows a complete diagram, in which admission takes place at 
A, as represented by the angle A — — X, while cut-off takes place at C, 
as given by the angle C — — X. In this figure, the steam lap and steam 
lead are represented respectively by the distances — N' and N' — N. 

In practical construction, it is not possible to have a steam port wide 
enough to give full opening to the exhaust, so that the width of this port 
must be marked off, as in the figure, by the arc W — W, the length of 
the line L — W representing to scale the width of the port so that the 
exhaust port is open wide when the crank is in the position — W, and 
remains open until it reaches the position — W. If this same width 
of the steam port be laid off in addition to the lap on the diameter of 
the steam valve circle, the point for the port to be wide open will fall 
at E' in the figure, thus showing that this port can never be fully open 
since the distance — E' that the valve would have to travel is greater 
than its maximum displacement. 

From this it is to be seen that when the valve has moved to give the 
steam port its maximum opening, the left-hand end of the valve overlaps 
the right-hand end of the port by an amount equal to the distance E — E' 



A STUDY OF THE ZEUNER SLIDE-VALVE DIAGRAM 



35 



in the figure. Fig. 31 is the diagram for tlie head end of the cylinder, 
the diagram for the cranlv end being similar, with the exception that the 
laps are different. 

In Fig. 31 is shown the prol)al)le form of indicator diagram that would 
be obtained from an engine represented by the valve diagram shown. The 
points of admission, cut-off, dead center, release, compression, etc., of the 
valve diagram are projected down to the corresponding points of the in- 
dicator diagram. A base line is then established, and the probable line 




FIG. 31. 



of vacuum is laid off on a vertical scale of pressures on which the boiler 
and admission pressures are also laid off at proper height for the assumed 
boiler pressure available. In this way, the points where the curvature of 
the diagram boimdary changes are determined, and smooth curves are 
sketched in by eye to make connections. 

Diagrams of this kind are of service principally in designing the en- 
gine, but they may be of considerable use in every-day work, by showing 
approximately what shape the diagram, taken with the indicator, should 
have. This is especially the case with high-speed engines with which it is 
often difficult to know whether or not the diagram taken with the indi- 
cator represents the actual performance of the engine. In some cases there 
are forces at work which distort the diagram of the high-speed engine 



36 VALVE SETTING 

until it is difficult to recognize the different valve operations. Sometimes 
the freaky diagrams are the result of irregular expansion and contraction 
of the valves, ports, and steam passages, with the engine at different tem- 
peratures, as after running some time or when just starting up. 

Altogether, there are twelve points of information given by the kind of 
valve diagram shown in Fig. 31, those not already mentioned being the 
angle of advance E — — U ; the travel of the valve X — — Y ; release 
at B, given by the angle B — — Y ; compression at D, given by the angle 
D — — X ; the exhaust lap — L ; the exhaust lead F' — U ; and the maxi- 
mum opening. 

In any consideration of the valve by the diagram, it is necessary that 
the points of admission and cut-off, as well as the point of compression 
and the exhaust lap, be given in terms such that they may be laid down 
on the diagram by angular distances of the crank from the beginning or 

end of the stroke. If, as is some- 
times the case, these items of in- 
formation are given as taking place 
at a certain part of the stroke, it 
will be necessary to find the angular 
positions corresponding to the data 
given by drawing a crank circle or 
a circle of reference on a new 
scale. In doing this, it is most 
convenient to draw the circle con- 
centric to the valve diagram. 
FIG. 32. As an example, suppose that the 

cut-off is given as at five eighths of 
the stroke; the crank circle is then drawn as in Fig. 33, so that the dis- 
tance C — P3 represents, to the selected scale, the stroke of the engine. 
The distance C — A is then laid off equal to five eighths of C — P^ and 
with a radius corresponding, by the selected scale, to the length of the 
connecting rod and with the center at B, an arc is swept from A to P. 
The angle C — — P thus formed is the angular distance from the begin- 
ning of the stroke at which cut-off takes place. This angle is then trans- 
ferred to the valve diagram and any remaining angular distances still 
unknown are found and transferred in the same manner. 

It will be noted that the different points of information given by the 
diagram appertain part to the steam side and the others to the exhaust 
side of the valve, while the angle of advance and the valve travel are 
common to both sides. In order to construct a complete diagram, it is 
necessary that four of these points of information be given, although for 
the construction of either the steam or exhaust side alone three points 
■will be sufficient. Where the complete diagram is to be constructed, one 




A STUDY OF THE ZEUNER SLIDE-VALVE DIAGRAM 37 

or two of the points given must belong to a different side of the diagram 
from the others, and one of the points must be a linear measurement, such 
as the steam lap, steam lead, or maximum opening; otherwise, as can 
readily be seen, the angular measurements could be used to construct a 
valve of any given linear dimensions provided only that the different 
measurements bear a certain relation to each other. Since the opening 
to exhaust is greater than that to steam, and since the ports can only be 
made sufficiently wide to allow full opening, the width of port when given 
as part of the data in any problem may be taken as the maximum opening 
of the exhaust port. 



IV 



THE RIDING CUT-OFF VALVE 



This chapter has to deal with what is known as the Meyer cut-off valve 
of which there are in use a few different modifications of design, such 
as: (a) Single valve and cut-off set over the ports in a midposition be- 
tween the ends of the cylinder; (&) valves bridging ports at each end 
of the cylinder operating as one; (c) separate valves over each steam 
valve port, and separate valves over the steam and exhaust cylinder ports. 

The cut-off valve operating in conjunction with the main steam valve, 
or valves, may be riding over or inside cut-off, but the action must be the 
same in principle. The only difference is that with more valves used a 




FIG. 33. 



FIG. 34. 



shorter steam port and independent and closer adjustment of action is 
secured. 

It is the purpose of this chapter to treat only of the simplest of Meyer 
cut-off valves, of which Fig. 33 is an illustration. This valve may be so 
constructed and connected that it may cut off the steam at a fixed and 
unvarying point, or by means of a hand wheel vary that point, to offset 
variations in boiler pressure, as in marine work; or where regularity of 
speed is essential, the cut-off valve may be operated from a shaft or other 
governor, the main valve being operated from a fi:xed eccentric. 

In the case under discussion the main valve and the cut-off valve are 
each driven by a separate fixed eccentric. The resemblance of the Meyer 
cut-off valve, in this connection, to the D slide valve is shown by compar- 
ing Figs. 33 and 34. 

The main valve of the Meyer combination, Fig. 33, controls the lead, 

38 



THE RIDING CUT-OFF VALVE 



39 



latest point of cut-off, the exhaust, and the compression. The cut-off 
valve controls the point at which expansion shall begin. Comparing the 
two valves placed in mid-position of their travel, it will be seen that the 
edge h of the main valve will cut off the steam from the cylinder the 
same as the edge K of the common slide valve, Fig. 34. Also, the edge 
J of the one valve should act the same as the edge J of the other, pro- 
viding the eccentrics are in the same relative positions. The same applies 
to the exhaust edges of each valve, M and N. The edge h will cut off 
steam from the port 6 independently of any action of the cut-off valves. 

The longest distance at which steam is admitted is controlled by the 
main valve, and the work of the cut-off valve is to cut off steam at some 
earlier point in the stroke. This it does by the edge G of the cut-off 
passing over the edge g of the port L, and on the other stroke the edge n 
of the cut-off passing over the edge n of the port K. 

Action of the Valves 

For example, let the steam ports be 1 in. wide, both in the valve and 
the cylinder, and the main valve have a steam lap of -| in., which will 
give the main valve a cut-off at about nine tenths of the stroke; and if 
the travel of the main valve be just sufficient to open fully the steam 
ports, the action of the main valve will not be imduly distorted by ex- 
cessive lap or over travel. Assuming that the main steam valve and cut-off 
valve when in midposition leave the edges n and G of the cut-off valve 
equidistant from the nearest edges of the main valve, i.e., one half the 
width of the steam port, take these as average conditions and follow the 
movements as follows : 

In Fig. 35, the crank (the travel being represented by the circle), is 
on its dead center at the crank end B\ the cut-off eccentric in this ex- 





FIG. 35. 



ample being set exactly opposite at N and the main eccentric at M, the 
main valve having no lead. It will be seen that the valves moving in the 
direction denoted by their arrows, while the crank starts in the direction 
shown by its arrow, the admission of steam will occur through the ports 
K and a uninfluenced by the cut-off valve. 



40 



VALVE SETTING 



Fig, 36 shows the position of the valves, eccentrics, and crank at the 
point of cut-oif. The crank being at half stroke, the cut-off is performed 
by that valve independently of the action of the main valve. 





FIG. 36. 

Fig. 37 shows the position of the valves and eccentrics at the point 
of exhaust release on the same end from the port a, thus completing the 
action of the valves for one piston stroke. 

Fig. 38 represents the same valves at one point in the processes shown 
in the previous figures. It is to illustrate the point that the effective area 



N 




M 




FIG. 37. 



of admission of steam through the valve port K to the cylinder port a 
is governed by the action of the cut-off valve. 

In this case, where the eccentrics are set as they are, the cut-off valve 
moves across the main valve port K before the latter valve has cut off, 




FIG. 38. 



FIG. 39. 



thus reducing the effective port area. This condition must be considered 
to obtain the most effective use of the valves and a change in position of 
eccentrics to get the quickest action of the valves at the proper time is 
desirable. 

Eccentrics are set as in the foregoing examples mostly on engines 



THE RIDING CUT-OFF VALVE 



41 



where a reversing of direction of rotation is wanted. But where the direc- 
tion of travel is constant, a greater latitude of position of the eccentric 
is allowed and taken advantage of in greater or lesser degree by various 
builders. Assume that we still have valves with the same amount of lap, 
etc., as already shown, and study the effects of change of position of the 
eccentric by a few more illustrations. 

In Fig. 39 the circle represents the travel of the crank and eccentrics. 
The crank is on dead center B, ready to start in the direction of the 
arrow; is the throw line of the crank N of the cut-off eccentric and 
M of the main eccentric, N being 169 degrees ahead of the crank and 59 




y X 




FIG. 40. 



degrees ahead of the main eccentric, the angular advance of which is 20 
degrees. 

Fig. 40 represents the position of the valves and eccentrics at the point 
of cut-off. Bearing in mind the position of the eccentrics before illus- 
trated, note the action of the same as shown in this figure. In passing 
the point X the eccentric moves the valve quickest on this stroke. It will 
then be seen that the cut-off valve has moved its fastest while near cut-off 
and the eccentric was passing this point; at the same time the main valve 
has not come to its best speed. 

Then noting Fig. 41, which shows the relative positions at point of 
cut-off of the main valve, it is seen that the two valves have been travel- 





-_x.-^ 



FIG. 41. 



ing at nearly the same speed while making the cut-offs, with the cut-off 
valve going the fastest at the right point and slower than the main valve 
after the latter has closed the cylinder port, thus shutting out the possibil- 
ity of reopening by the main valve's catching up and passing the cut-off 
before the main valve has cut off. 



42 VALVE SETTING 

The main valve is traveling faster in Fig. 41 for the added reason that 
it travels faster while the eccentric is moving up to the point X than 
after it leaves it, for any given distance of the eccentric travel on that 
stroke. To illustrate this point, refer to Fig. 43, in which the circle rep- 
resents the eccentric travel, the line L — L the line of valve travel, M the 
position of the eccentric 35 degrees ahead of the point X, and N the posi- 
tion of the eccentric 35 degrees the other side. 

Setting a pair of compasses to represent the length of the eccentric 
rod, place one point at M and mark on the line L — L the arc 0; next 
set one point at X and scrihe the are P ; then with one point at N, scribe 
arc Q. The distance from to P is the distance the valve traveled while 
the eccentric moved from M to X, and the distance from P to ^ is the 
distance the valve traveled while the eccentric moved from X to N. The 
difference in valve travel while the eccentric traveled equal distances from 
X is shown by the arc r. This will illustrate why the cut-off valve must 





FIG. 42. FIG. 43. 

travel at least as fast as the main valve from the position shown in Fig. 
40 to that shown in Fig. 41. 

Now comes the question of length of the eccentric rod. Assuming that 
in all the cases spoken of in this article an engine of 20-in, stroke were 
used, it will be found that in the case of setting the cut-off eccentric 
exactly opposite to the crank, the cut-off of steam occurred at 9 ins. of 
both strokes, while in the case where the cut-off eccentric was set back 
11 degrees in Fig. 39 the cut-off of steam is delayed to the thirteenth inch 
of one stroke and the sixteenth inch of the other, delaying the cut-off in 
both strokes and making it unequal. The additional reason for this latter 
condition is that in this case the cut-off eccentric has been set back and 
its rod made of such length as to get the longest point of cut-off without 
a reopening. 

To equalize the points of cut-off it is necessary to move the cut-off 
eccentric back more and shorten the rod. In Fig. 43, for example, the 
positions of the valves are shown at the time the piston is on the thirteenth 
inch of its motion on the back stroke (this being the point of cut-off for 
the other stroke), and it is shown that the steam port L is not yet closed. 
If, to close it, the cut-off eccentric be moved ahead, it will hasten the 
point of cut-off for the other stroke, and if we lengthen the rod to close 



THE RIDING CUT-OFF VALVE 



43 



L, it will delay the point of cut-off for the other stroke, and that would 
in this case cause a reopening. 

The course to pursue is to change the position of the eccentric and 
the length of the rod as well, adjusting the two until the ports just 
escape reopening and the cut-off is equal. In this way the longest possible 
equalized points of cut-off are obtained. 

Allowing that in every change of position of the cut-off eccentric a 
corresponding change of length of rod must be made : Referring back to 
Fig. 40, with eccentrics set as here (and the two valves moving together 
after the point of cut-off), the cut-off valve will not act on the forward 
stroke after the thirteenth inch of piston stroke, and since the main valve 
cuts off after the eighteenth inch of the stroke, therefore no cut-off can be 
effected between these points. 

That this cannot be remedied by moving the cut-off eccentric may be 
shown as follows : Referring again to Fig. 40, if the cut-off eccentric were 
moved farther ahead, increasing its angle of 169 degrees, the cut-off 
would occur earlier, while if the angle were diminished, the cut-off would 
not be effected by the cut-off valve, because it would not fully cover the 
port. 

This will be seen by reference to Fig. 44, in which the cut-off eccentric 
is moved closer to X, and as a result the cut-off is effected by the main 



^**^ — •-. 




FIG. 44 



valve. Finally if the cut-off eccentric were moved to the position X, Fig. 
45, at the time the main eccentric stood at M, the cut-off valve would not 
effect the cut-off at all. The cut-off eccentric is thus shown to be in posi- 
tion to cut off at the latest possible point, without reopening the port, as 
shown in Fig. 40. 

Having limited the position of the cut-off eccentric in one direction, 
the next step is to find how far it can be set to cut off as early in the 
stroke as possible. 

In the foregoing examples the cut-off was set at 180 degrees from the 
crank, or at a lesser angle ahead of the crank, but it may be set at some 
angle behind the crank instead of ahead of it. It is understood that 
aliead means less than 180 degrees ahead of the crank in the direction. 



44 



VALVE SETTING 



of rotation, and behind the crank is less than 180 degrees in the direction 
opposite the direction of rotation from the crank. 

In Fig. 4:6, for instance, it is set at 90 degrees behind the crank, the 
valve lap and travel remaining the same as before, the crank B on " dead 





FIG. 46. 



center," the main valve having no lead, and the port a being closed. In 
Fig. 47 are shown the positions at the point of cut-off, the crank having 
moved but 22 deffrees. 





FIG. 47. 



On continuing the motion, the ports will arrive at the position shown 
in Fig. 48, from which it will be seen that the cut-off eccentric being 
at N, and the main eccentric at M, and the crank at B, the movements 
of the two valves would be in opposite directions. The cut-off valve will, 
therefore, keep the port K closed until the valves again change direction 
and approach the positions shown in Fig. 46; and it is clear that if the 





FIG. 48. 



cut-off eccentric were set at less than 90 degrees behind the crank, the 
cut-off valve would first effect the cut-off, then lag behind and reopen 
the port K. In Fig. 49, for example, the cut-off eccentric has been ad- 
vanced to 86 degrees behind the crank, and the cut-off valve after having 



THE RIDIiNG CUT-OFF VALVE 45 

cut off the steam lags behind and has begun its return stroke, allowing 
the ports to reopen and live steam to reenter, as denoted by the arrow. 
Therefore, the least possible angle behind the crank for a cut-off valve 
is 90 degrees. These are the principal points to be understood and should 
be quickly grasped when ready to set these valves. 

The ranges of angle of advance for both the main and cut-off valves 
here given are the maximum in either direction. In engineering prac- 
tice, various builders vary the amount of advance and valve lap, but it 
is within this range. Some designers have less lap than herein given, 
say 25 per cent, of lap, and so adjust the position of the eccentrics that the 
cut-off will conform to the condition of the lap. In a multiported cut-off 





valve is exhibited the greatest degree of perfection, as it gives a maximum 
opening with a minimum lap. 

It is not the writer's purpose to go too deeply into the design of this 
valve, only just sufficiently to set the valves with the hints that follow. 
Before going further, however, it is well to dwell on the principal points 
already brought out: 

First, all classes of the Meyer cut-off valve are similar in action to 
the D slide valve, and easier to set for complicated conditions. 

Second, Figs. 35, 36, 37, and 38 have to deal with single valves and 
eccentrics, with the cut-off set exactly opposite the crank. Such valve 
and eccentric arrangement is found mostly on marine engines, sometimes 
using a hand wheel. The use of the hand wheel on the valve stem gives 
the effect of more or less lap. 

Third, where the direction of rotation is constant, and especially in 
stationary practice, a modification of the position of the cut-off eccentric 
is more desirable and is varied, as shown by Figs. 39, 40, 41, 42, 43, 44, 
45, 46, 47, 48, and 49. Where the lap is 50 per cent, of the port, the 
following facts are to be remembered in locating the position of the eccen- 
tric : That to get a cut-off later than one-half stroke, the eccentric must 
be set less than 180 degrees hefore the crank down to 169 degrees before 
the crank (no less), as shown in Figs. 39. 40, and 41. To get a cut-off 
at earlier than one-half stroke, the eccentric must be set at less than 180 
degrees behind the crank, down to 90 degrees behind the crank (no less), 
as shown in Figs. 43, 44, 45, 46, 47, 48, and 49. 



46 



VALVE SETTING 



Fourth, the multiported valves may change this so that in some cases, 
with small lap, an early cut-off may be secured with the eccentric less 
than 180 degrees ahead. 

Fifth, in engines equipped with multiported valves, the length of rods, 
eccentric travel, and valve lap are all attended to by the designer, so that 
the essential for the engineer in charge (after wear has set in and slipped 
eccentrics are a possibility) is to know the proper position of the eccen- 
tric and how to locate that point practically with all the gear mounted on 
the engine. 

Sixth, with all cut-off valve gear the main-valve action is first looked 
into, and its action is to be considered the same as in any D slide valve. 
Then the cut-off valve is to be considered as the steam edges only. 

To Set the Valves 

On all engines, when preparing to set the valves, the first thing is to 
find and adjust all lost motion in the valve gear, then proceed to place 
the engine on the " dead center." Owing to the fact that the crosshead 
will remain stationary a short time before the crank pin passes the center, 
and remain so until the crank has passed the center a short distance, it 
is best to take greater care than to simply note the point where the cross- 




FIG. 50. 



head rests at the end of the stroke, in order to find the " dead center." 
The writer believes the process illustrated in Fig. 50 is an accurate process. 
In the figure, J and K represent two crosshead guides, L the cross- 
head, M the path of crank travel, N and the center lines 'of the con- 
necting rod at different positions, and P the balance wheel. To start 
with, make a tram S out of any material convenient, preferably round 
steel. Turn the engine around until the crank is at the point B in any 
position where the crosshead is still moving with the other parts, near the 
end of the stroke. Then place mark A on the crosshead, running the 



THE RIDING CUT-OFF VALVE 47 

mark up close to nearest or most convenient guide bar. (Whore the 
crosshead is down in the frame of the engine, use a straight edge across 
the top of the holding-down bars.) Then place mark C on the guide bar 
opposite the mark A on the crosshead. Now, with the tram S (one point 
on the given mark on the floor opposite the fly wheel, and on a line with 
one edge of the rim) scribe the mark D on the face or side of the rim, 
making the arc come to the edge in either case. 

Next turn the engine so that the crank passes the center and the 
mark A on the crosshead again comes to the mark C on the guide bar. 
Then take the tram, again resting it on the same point on the floor, and 
scribe the arc to the mark F on the same edge of the rim of the wheel. 
The crank will then be at E. 

Now place prick-punch marks as near the edge as possible at the points 
D and F, and with a pair of dividers bisect the distance from D to F and 
make the mark G. Turn the engine back so that with the tram resting 
at the same point on the floor, the other point of the tram will touch G. 
The crank will then be on " dead center " at I, and the mark A on the 
crosshead will be opposite the mark H on the guide bar, which should 
be marked as the point where the crosshead reaches the end of the stroke. 

Turn the engine to the opposite end of the stroke and repeat the fore- 
going moves, when both " dead centers " will have been found and marked. 
Now, with a marking chisel go over all the scribe marks and make them 
permanent, and where the center punch marks are on the rim of the wheel, 
the floor and the frame, it is a wise precaution to place marks like this 
I I around the center punch marks. It is also a good means of finding 
the marks in future. 

The next move is to get the eccentric on " dead center." Where the 
eccentrics are fastened by set-screws, friction keys, or keys easily with- 
drawn, loosen up on one or the other, as the case may be, and turn the 
eccentric around the shaft while finding the centers. Where there is a 
fixed eccentric, as in governor eccentrics, the engine itself must be turned 
around to find the points desired. 

Make a tram A, Fig. 51, out of a board or sheet steel and place at the 
point indicated a nail or other pointed iron or steel, just far enough out 
so that arcs B C and D E can be scribed, bringing the arcs down to the 
edge of the eccentric at the points B and D. Care should be exercised, 
in using the tram, to have the end on the shaft or the boss of the eccen- 
tric the same distance away from the eccentric in both instances. Take 
a pair of dividers and from the points B and.Z) scribe arcs so that they 
will exactly intersect on the eccentric edge at F. This will be the center 
line of the eccentric. 

Make another tram G, Fig. 52, make a mark H with the center punch 
on the eccentric rod, and with one leg of the tram on the point H scribe 



48 



VALVE SETTING 



the ares J K and LM on the eccentric strap coming to the points J and L 
on the edge of the strap. With the dividers scribe from points J and L 
arcs exactly intersecting each other at the point N. 

With a marking chisel make permanent marks at the point F on the 
eccentric and the point N on the eccentric strap. Bring the eccentric 





FIG. 51. 

around so that both points correspond and the eccentric will then be on 
one " dead center." From the points J and L scribe the arcs P and 
Q R, ending at the points and Q on the edge of the strap. From the 
points and Q scribe arcs intersecting at the point 8 on the edge of the 
strap. With the chisel make a mark on the strap at S. Bring the eccen- 
tric around so that the point F corresponds with the point ;S^, and the 
eccentric will be on the opposite end of the travel. 

Now assume an engine equipped with the Meyer cut-off, substantially 
as in the illustrations, i.e., a single main valve and single cut-off, each 




FIG. 52. 



driven by one eccentric. Also assume that the builders have made all 
proportions, lap, width of ports, and bridges correct. Take out the cut-off 
valve and start to adjust the action of the main valve, bearing in mind it 
should be set practically the same as any D slide valve. 



THE RIDING CUT-OFF VALVE 



49 



Fig. 53 shows a steam chest with the valves removed. Take a scale 
and scriber and mark lines from the lower end of the ports A and C on 
the valve seat down to the bottom of the valve chest, and with an adjust- 
able square resting on the surface of the valve-chest flange carry out these 
lines to the points, a, h, d, and e on the valve-chest flange. Then bisect 
the distance between the inner edges of the steam ports, get a center line 




FIG. 53. 



through the middle of the exhaust port B and carry it out in the same 
way to the point c on the steam-chest flange. 

In Fig. 54 is shown the main valve in position, with the center line 
A corresponding with the center line c on the steam-chest flange. This 
shows the valve on the center of travel. 

With the main valve in position and connected up, proceed as shown 
in Figs. 51 and 52, and place the eccentric on the " dead center " nearest 



50 



VALVE SETTING 



the engine cylinder. With a seriber mark downward on the edge of the 
valve farthest from the eccentric, which will result in the line m on the 
valve seat (Fig. 53). Move the eccentric to a point opposite the center 
and scribe downward along the same edge of the valve, which will give 
line Tc on the valve seat. With the di^dders or scale locate and mark the 
line I on the valve seat, half way between the lines h and m. Then turn 




FIG. 54. 



the eccentric around until the same edge of the valve comes to the line I. 
The center line A on the valve should now correspond with the line c 
on the steam-chest flange, as shown in Fig. 54. 

With the valve in midposition, reach through its ports a and &, Fig. 
54, with a seriber and mark along its steam edges on the valve faces the 
lines i and ; (Fig. 53). 

Upon removing the valve again it can be seen what the lap is, and 



THE RIDING CUT-OFF VALVE 51 

whether it is even, by measuring from the line i to the nearest edge of 
the port A, and from the line j to the nearest edge of the port C. 

When it is impossible to see the valve seat with the main valve in 
position, so as to scribe the lines Jc, I, and m (Fig. 53) on the valve seat, 
proceed as follows : 

After marking the port lines and center on the valve-chest edge, as 
shown in Fig. 53, replace the valve and, placing the eccentric on the center 
nearest the cjdinder, with the scriber mark a line / on the valve stem 
where it leaves the stuffing-box gland. Placing the eccentric on the oppo- 
site center, mark a line /;, on the valve stem at the same point at the edge 
of the gland. Find and mark the line g half way between / and h and 
turn the eccentric so that the line g is just entering the gland. The valve 
should be on the center of its travel and its center line A, Fig. 51, should 
correspond with the line c. If this latter process is followed, care should 
be taken to have the stuffing-box gland pulled up so that it will not move 
in or out with any movement of the stem. 

In Fig. 54 the marks are sho'wii on the cut-off valve stem, as it is 
easiest seen, but the same application applies to both stems. 

ISTow place the engine on " dead center " and pull the eccentric around 
until the lead is given and then fix the eccentric in position. Pull the en- 
gine around to opposite " dead center," and observe the lead on that end. 
Make the lead the same on each end, or make the usual allowances for 
the crank end of a horizontal engine or the bottom end of a vertical en- 
gine, as determined by the builder. Place the cut-off valve in position 
connected up to valve stem. Use the same precautions on the cut-off 
eccentric as with the main eccentric to get " dead center." 

Then when the main valve is in midposition place the cut-off valve 
in the same position, and observe if tlie cut-off edges are the same dis- 
tance from the steam edges of the main valve. If they are, set the en- 
gine at one half its stroke. To do this, divide the distance H and R 
on the guide J, Fig. 50 (which distances denote the end of the stroke), 
so as to get point T. Let the mark A correspond to T. Now pull the 
cut-off eccentric around until the cut-off valve edge is line and line with 
the cut-off edge of the main valve. Set the cut-off eccentric and pull 
the engine over to one-half stroke, going in the opposite direction. Ob- 
serve if the cut-off is the same. If not, then the eccentric must be set 
ahead or back to even it up. 

With both eccentrics set and secured in place, turn the engine around 
and observe that there is no reopening of the cut-off valve after it has 
cut off and before the main valve has cut off. Bear in mind the points 
brought out as to position of the eccentrics and lap of the valves in refer- 
ence to cutting off before or after one-half stroke. 

Where cut-off valves are operated by automatic governors all the rules 



52 VALVE SETTING 

here mentioned are to be observed when the governor weights are resting 
at the inner position of their travel with everything connected up. After 
the valve setting is all done, the governor spring or springs should be 
disconnected and the governor parts blocked out to the other extreme 
position. Then while the engine is turned a complete revolution, it should 
be observed that the cut-off valve covers the main valve ports at all points 
of the revolution. For finer adjustment of the valves recourse must be had 
to the indicator. 



THE COELISS STEAM ENGINES* 

To equalize the clearance at both ends of the steam cylinder, place 
the crank pin upon its forward dead center, loosen the piston-rod nut, and 
screw the piston into the crosshead until it is brought up against the 
front head of the cylinder; after which screw up the nut until it touches 
the crosshead hub without jamming. Now place the crank pin upon its 
opposite dead center and back out the piston rod until the piston is forced 
against the back head, being careful not to disturb the position of the 
nut upon the rod. The distance between the face of the nut and cross- 




FIG. 55. 



head hub represents the total clearance of the cylinder, which should be 
adjusted by screwing the piston rod into the crosshead half of the amount 
of total clearance and tightening and the nut. 

This method is sufficiently accurate for all practical purposes if care 
is exercised not to disturb the position of the nut upon the rod. A better 
way if time permits is to mark in some convenient position upon the 
crosshead guide the stroke of the engine, obtained by placing the crank 
pin upon its opposite dead centers, scribing these lines coincident to the 
same edge of the crosshead shoe. Remove the connecting rod, and force 
the piston alternately against the back and front heads of the cylinder, 

* Contributed to Power, by John L. Flock. 
53 



54 VALVE SETTING 

scribing both positions upon the guide^ using the same edge of the cross- 
head shoe as before. The distance between these two marks will represent 
the stroke of the engine phis the total clearance; subtracting from this 
the stroke of the engine will give the total clearance of the cylinder. 

Now place the connecting rod in position with the crank pin upon the 
forward dead center and the piston against the. front head. Screw up the 
piston-rod nut until it touches the crosshead hub without jamming, and 
equalize the clearance by backing the piston rod out of the crosshead, a 
distance equal to half of the total amount of clearance, measuring be- 
tween the face of the nut and end of the crosshead hub, as before, and 
set up the nut. 

After the clearance has been ascertained a good plan is to place a 
center punch mark upon the piston rod and crosshead hub parallel to the 
axis of the cylinder, and make a gauge of |-in. round steel, the distance 
between the points of which equals that of the center punch marks. This 
gauge will be found of the greatest convenience should it at any time be 
necessary to dismantle the engine. All that is required to readjust the 
clearance on assembling the engine is to screw the piston rod into the 
crosshead, until the center punch marks coincide with the points of the 
gauge. 

To set the valves of horizontal Corliss steam engines, proceed as fol- 
lows : Take off the back bonnets and remove the valves. With a sharp 
chisel mark upon their back end a line, touching the circumference of 
the valves, coincident to the steam edges of the valves, and also place 
marks in some convenient position on the valve housings representing the 
edges and width of the steam ports, and replace the valves. Place the 
swing plate ajid rocker arm in a vertical position, with crank pin on its 
dead center toward steam cylinder, and mark the swing-plate hub, pro- 
longing the line upon the swing-plate bracket. Loosen the eccentric and 
rotate it, adjusting the eccentric rod so that the line upon the swing- 
plate hub vibrates equally distant each side of the line upon the swing- 
plate bracket, after which secure the swing plate in its vertical position 
by inserting several thicknesses of emery cloth under the washer of the 
swing-plate stud and tightening the nut. Give the steam and exhaust 
valves their required lap, using for this purpose a pair of dividers and 
measuring from the mark representing the cut-off edge of the port and 
steam edge of the valve on the circumference. After the steam and ex- 
haust rods have been secured for equal lap at both ends of the steam 
cylinders, release the swing plate and advance the eccentric forward upon 
the shaft, until the line representing the edge of the left-hand steam valve 
has traveled beyond the incision representing the cut-off edge of the port 
indicating lead, and secure the eccentric to the shaft.' The engine should 
now be rotated and the marks upon all four valves carefully gone over, 



THE CORLISS STEAM ENGINES 55 

to ascertain whether the lead is equal at both ends and the valves have 
sufficient overtravel to prevent wire drawing at early cut-off. Half-inch 
overtravel with j\ in, lead will be found adequate for the majority of 
engines; the steam lap should be from ^ to f in., with exhaust lap rang- 
ing from -^ to j^g i^-? depending • upon the size of the engine and the 
amount of compression required. The lead of the exhaust valves should 
always be in excess of that of the live steam valves, so that just on the 
point of opening the live steam valves still have lap to prevent the blowing 
through of steam. This completes the setting of the eccentric, rocker arm, 
swing plate, and steam and exhaust valves as far as can be done without 
the use of an indicator. 

Adjust the coupling rod between the governor weight bar lever A so 
that it oscillates equally out of its horizontal position when the governor 
balls are brought into its highest and lowest position. 

When the steam engine is to be started, the steam, cylinder must be 
able to receive the full steam pressure, and the steam valves must not be 
tripped. To enable this to be done, governors of Corliss engines are sup- 
plied with a loose collar D having a slot E fitted to the governor banjo, 
or a loose pin which is fitted to a series of holes and performs the same 
functions as the collar. 

When the governor balls have attained their normal position, the collar 
should be set so as to allow the lifting sleeve F to sink below the upper 
edge of the collar into the slot E. If a pin is used, it should be removed 
for the same purpose. The reason for this is obvious, for should the gov- 
ernor belt break while the governor is in this position, the trip rods B 
and C will place the safety toes G in such a position as to permanently 
unhook the live steam valves, and the engine will stop. When starting, 
the collar or pin is placed so that the safety toes are out of action. 

To adjust the trip cams H and safety toes G, place the governor lift- 
ing sleeve upon the top of the collar D as in the position for starting 
the engine, rotate the crank shaft so that the eccentric is in its extreme 
forward position, as shown in the drawing. The correctness of this posi- 
tion is assured by referring to the marks upon the swing-plate hub and 
bracket. The mark denoting the vertical position of the swing plate 
should now coincide with that upon the bracket representing the forward 
travel of the swing plate. Shorten or lengthen the trip rod B, as the 
case may be, so that the trip cam H will just touch the block upon the 
latch hook without disengaging the hook from the latch block upon the 
steam lever, but will do so, allowing the valve to cut off, when a piece of 
iron or wood, ^ in. thick, is inserted between the top edge of collar D 
and governor lifting sleeve F. 

Set the safety toe G in such a position as will fully and securely un- 
hook the live steam valve when the collar D is turned for regular running. 



TABLE SHOWING PRINCIPAL DIMENSIONS AND HORSE POWER OF CORLISS ENGINE 
WITH DIFFERENT STEAM PRESSURES AND POINTS OF CUT-OFF 





3 


01 


Boiler Pressure 


Boiler Pressure 


Boile 


r Pressure 


B 


and Wheel 






■n 


a 


* 

C 

o 


Pipe 1 




a 


0) 


90 Pounds 


100 Pounds 


125 Pounds 










1-1 




h; 


s 

a 


S 




a 








•a 


u 

(S 

p. 

CO 


<0 C 
















0) 

o 


Weight 




a 

ei 
4) 


S 


3 


1 


5 


3 
J3. 


w 















(V 

m 


_o 

3 

"o 
> 

(U 


a 

O 


Point of Cut-off 


Point of Cut-off 


Point 


of Cut-off 


5 


\^ 




'a a 






\A 


la 

"u ■ 


M 


«' 




1-5 


1-4 
45 


1-3 

55 


1-5 
43 


1-4 


1-3 


1-5 


1-4 


1-3 


Ft. 


In. 


Pounds 


Pounds 


Inches 


In. 


II 


10X20 


120 


400 


38 


53 


62 


56 


63 


77 


7 


13 


4,500 


10,500 


\ 


-h 


-h 


1| 


2h 




10X24il20 


480 45 


54 


66 


51 


61 


74 


66 


75 


92 


8 


13 


5,000 


12,270 








" 


3 




10X30 lOOi 500 


47 


57 
52 


69 
63 


54 
52 


64 

62 


78 


70 


79 


96 


8 


13 


5,400 


13,250 




— 


— 


li 


3 
3 


- 


11X20|120 400 


46 


75 


68 


76 


93 


8 


13 


6,000 


14,000 


" 


11X241201 480 


55 


67 


82 


62 


74 


89 


71 


83 


101 


8 


13 


7,000 


14,600 


*' 






" 


3 




11X30 100 


500 


57 


69 


84 


65 


77 


94 
106 


84 
96 


95 

107 


116 
131 


8 
9 


13 


7,800 


18,000 










3 




12X24 120 


480 


65 


78 


95 


74 


87 


13 


9,100 


19,300 


" 




2 


3 




12X30, 90 


450 


62 


74 


90 


69 


83 


101 


89 


102 


144 


9 


13 


10,000 


21,100 A 






" 


3 




12X36 85 


480 


70 


84 


102 


78 


94 


114 


101 


116 


152 


10 


15 


10,300 


22,500 


** 


Ti 


u 


2i 


3i 


- 


14X28' 95 


443 


78 


93 


114 


90 


105 


128 


112 


130 


156 


10 


15 


10,500 


22,800 


« 


14X32; 90 


479 


85 


100 


122 


97 


114 


138 


120 


140 


170 


10 


15 


10,800 


26,500 


" 






2i 


3i 




14X36; 85 


510 


95 


114 


139 


107 


128 


156 


137 


158 


193 


10 


19 


11,000 


28,500 


" 






2^ 


3i 




14X42 82 


574 


107 


128 


156 


120 


144 


175 


154 


178 


217 


11 


19 


11,400 


29,100 


i 




-. 


2 


3i 
4 


" 


16X32 90 


479 


110 


132 


161 


126 


149 


182 


158 


184 


224 


12 


21 


12,000 


29,100 


« 




16X36; 82 


492 


120 


144 


175 


135 


162 


197 


173 


200 


244 


12 


21 


12,300 


29,400 


" 






91 


4 




16X42 78 


546 


133 


159 


194 


150 


179 


218 


192 


221 


269 


12 


23 


12,600 


34,800 


(( 






2^ 


4 




16X48 75 


600 


145 


176 
177 


215 
216 


165 


199 


242 


215 


245 
246 


299 
300 


12 
12 


25 


13,000 


34,840 
34,900 


1 


— 


— 




4 




18X36 


80 


480 


148 


166 


199 


242 


214 


25 


14,000 


2^ 


5 




18X40 


80 


533 


156 


185 


225 


179 


210 


256 


222 


258 


312 


12 


25 


14,600 


36,000 








2| 


5 




18X42 


78 


546 


168 


202 


246 


189 


227 


277 


244 


281 


321 


14 


25 


15,000 


37,900 


" 






" 


5 




18X48 


75 


600 


185 


222 


271 


208 


249 


504 


268 


308 


376 


16 


25 


16,000 


42,900 




— 


— 


2^ 


5 

5 


- 


20X40 


80 


533 


192 


228 


278 


220 


257 


314 


273 


317 


385 


16 


25 


17,000 


45,500 


20X42 


75 


525 


200 


240 


292 


225 


270 


329 


289 


333 


406 


16 


31 


18,000 


48,300: " 
50,150 " 






2^ 


5 




20X48 


72 


576 


219 


263 


321 


246 


296 


361 


317 


365 


445 


16 


31 


20,000 






3 


5 




20X60 


65 


650 


248 


297 


362 


279 


334 


407 


358 


413 


504 


14 


33 


20,800 


51,000| " 






u 


5 




22X36 


100 


600 


262 


310 


380 


300 


350 


427 


373 


435 


531 


16 


31 


21,300 


51,900 11 






2i 


6 




22X42 


75 


525 


242 


290 


343 


271 


326 


398 


350 


403 


491 


14 


33 


22,000 


53,6£0l " 






2^ 


6 




22X44 


80 


586 


256 


304 


370 


292 


343 


418 


361 


425 


518 


14 


37 


23,000 


56,600 " 






2^ 


6 




22X48 


72 


576 


265 


318 


388 


298 


358 


437 


385 


443 


540 


16 


37 


24,000 


60,000 " 








6 




22X60 


65 


650 


299 
314 


359 


433 


336 


404 


493 


433 


499 


609 


16 


31 


24,500 


61,i00| " 






2i 


6 

7 


- 


24X36 


100 


600 


371 


455 


360 


420 


512 


445 


520 


634 


16 


37 


25,000 


62,500' " 






24X42 


75 


525 


287 


347 


423 


323 


392 


478 


420 


482 


588 


16 


40 


26,000 


64,000 -h 






2| 


7 




24X48 


70 


560 


307 


368 


448 


345 


414 


505 


444 


511 


723 


16 


40 


27,000 


81,300 " 






2i 


7 


1 


24X52 


75 


619 


338 


400 


490 


386 


450 


550 


480 


560 


683 


16 


40 


26,300 


84,500 " 








7 




24X60 


65 


650 


356 


427 


520 


401 


481 


587 


515 


594 


724 


18 


40 


28,000 


90,000 


— 


■h 


— 


ii 


7 




26X36 


100 


600 


366 


433 


530 


420 


490 


598 


520 


607 


740 


18 


40 


29,000 


90,500 


2\ 


7 


] 


26X48 


70 


560 


360 


432 


527 


405 


486 


593 


521 


600 


732 


16 


40 


32,000 


92,000! " 




h 


" 


7 


_ 


26X52 


75 


649 


395 


469 


572 


454 


530 


646 


560 


655 


799 


16 


40 


30,000 


92, 000 1 " 






" 


7 


, 


26X54 


70 


630 


404 


455 


555 


455 


546 


661 


592 


672 


820 


16 


40 


31,500 


92,500 " 






2i 


7 


. 


26X56 


70 


522 


398 


472 


575 


457 


533 


650 


563 


659 


804 


18 


40 


36,000 


93,600 " 








7 


. 


26X60 


65 


650 


418 


502 


612 


470 


564 


688 602 


693 


845 


18 


40 


34,000 


94,000 " 








7 


. 



*Distance of piston from end of stroke in inches. 



IBLE SHOWING PRINCIPAL DIMENSIONS AND HORSE POWER OF CORLISS ENGINES 
WITH DIFFERENT STEAM PRESSURES AND POINTS OF CUT-OFF— Continued 





3 


01 

ft 


Boiler Pressure 


Boiler Pressure 


Boiler Pressure 


Band Wlieel 






1 


a 


* 

C 

o 


Pi 


pe 


0) 








100 Pounds 


125 Pounds 




c S a) 


5* 


H-1 


^ 


I 


F 




a 










a 


ft 

c 



_3 

"o 

> 

a; 


.■2 

-0 3 

ftS 

c 
o 








a 




Weight 


t;'^ 


S 


s 

1 


3 




03 

Q 
S 

OJ 


"S . 


"o 


Point of Cut-off 


Point of Cut-off 


Point of Cut-off 






1-5 


1-4 


1-3 


1-5 


1-4 


1-3 


1-5 


1-4 


1-3 


Ft. 


In. 


1 Pounds 


Pounds 


Inches 


In. 


In. 


X36 


100 


600 


488 


678 


827 


560 


055 


809 


693 


810 


988 


18 


40 35,000 


94,800 


-iV 


t^f 


T)^ 


21 


8 


10 


X48; 68 


a44 


406 


487 


594 


457 


548 


668 


588 


677 


826 


18! 401 34,000 


95,000 








8 


10 


X52 


75 


649 


460 


545 


665 


525 


616 


751 


652 


760 


927 


18 


40 35,000 


94,500 


« 


" 


It 


3 


8 


10 


XM 


70 


630 


469 


563 


696 


528 


624 


761 


686 


768 


937 


18 


40! '37,000 


95,000 


" 


« 


tt 


tt 


8 


10 


Xa6 


70 


522 


463 


;)48 


669 


528 


620 


755 


657 


765 


933 


18 


40 37,500 


94,500 


" 


" 


ti 


11 


8 


10 


X60 65 


650 


485 


582 


710 


545 


654 


804 


700 


807 


968 


20 
20 


40 


36,000 


137,000 


(4 


" 


" 


3i 


8 


10 


X36 


100 


600 


488 


678 


700 


560 


655 


795 


693 


810 


970 


40 


37,600 


138,000 


a 


u 


tt 


ti 


8 


10 


X4S 


68 


544 


466 


559 


682 


542 


629 


773 


674 


776 


931 


20 


40 


38,000 


140,000 


¥■ 


" 


A 


It 


8 


10 


K62 


75 


700 


528 


626 


765 


599 


710 


862 


752 


876 


1057 


20 


40 


38,400 


140,000 




" 




It 


8 


10 


XM 


70 


630 


538 


646 


788 


607 


727 


894 


789 


970 


1164 


20 


40 


39,000 


141,500 


'' 


" 


tt 


^ 


8 


10 


Xi)6 


70 


653 


53£> 


633 


774 


605 


718 


872 


760 


886 


1070 


22 


40 


38,000 


144,500 


" 


« 


tt 


8 


10 


K6U 


62 


620 


531 


637 


777 


597 


717 


882 


770 


886 


1063 


22 


40 


40,000 


149,000 


" 


" 


" 


it 


8 


10 


KV2 


5o 


660 


5bo 


678 


82/ 


635 


762 


937 


817 


942 


1130 


22 


40 


41,000 




" 


" 


" 


3f 


8 


10 


<48 75 


600 


555 


658 


802 


628 


745 


905 


790 


920 


1110 


22 


54 


42,000 




a 


^4 




„ 


10 


12 


<52 


75 


700 


600 


712 


870 


680 


807 


980 


853 


996 


1195 


22 


54 


43,200 




« 






tt 


10 


12 


<56 


70 


653 


608 


720 


880 


687 


814 


990 


862 


1005 


1216 


22 


40 


44,000 




" 


" 




tt 


10 


I'' 


<6U 


62 


620 


604 


725 


885 


680 


816 


996 


975 


1007 


1208 


22 


40 


45,000 




(( 


" 


« 


a 


10 


1"^ 


<V2 
<48 


55 
65 


660 


643 


772 


926 


723 


868 


1058 


931 


1073 


1288 


22 54 


49,000 




u 


« 


" 


4 


10 


12 


520 


572 


686 


823 


644 


772 


942 


828 


954 


1145 


22 


54 


53,500 




a 


« 


tt 


it 


10 


1'> 


<6U 


62 


620 


682 


818 


981 


767 


920 


1122 


987 


1137 


1364 


24 


60 


50,000 




« 


« 


tt 


3i 


10 


I*? 


<V2 


55 


660 


726 


871 


1045 


817 


980 


1195 


1051 


1211 


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♦Distance of piston from end of stroke in inches. 



58 VALVE SETTING 

but will not do so when set for starting, Eeverse the extreme position 
of the eccentric and adjust the trip rod C as described for B. 

Set the length of the dashpot rods so that when the swing plate is in 
its extreme position to the right, the cut-off toe of valve K is in the mid- 
dle of both stops provided on its disengaging lever. The first stop is that 
which lifts the dashpot piston; the second stop is the one which will bring 
the dashpot piston to its lowest position in case it has not assumed it 
of its own accord, and when the swing plate is in its extreme position to 
the right, the cut-off toe of the valve L is in the middle of both stops 
on its respective disengaging lever. The dashpot should be well lubri- 
cated, being careful that the quantity supplied is not sufficient to choke 
the air passages, for by so doing the dashpot is liable to be broken when 
the dashpot plunger drops. The air-regulating valve should be adjusted 
so that the plunger will drop sufficiently to allow the latch hook to engage 
the cut-off toe upon the steam lever without striking the bottom of the 
dashpot. Should the plunger descend too quickly the valve should be 
regulated until the required speed is attained. When carrying steam full 
stroke (not cutting off), the regulating valves should be opened to relieve 
the steam valves from the additional strain transmitted by the dashpots. 
If the governor is equipped with an oil dashpot, it should be kept full 
of a not too heavy oil. If this is neglected, the governor will have an 
irregular motion in jerks corresponding to the height of the dashpot not 
occupied by the oil. The tension of the governor belt should be sufficient 
to prevent any tendency to slip if smooth, regular running is to be 
assured. 

When the various parts of a Corliss valve gear are in their proper 
adjustment, the reach rod should be of such a length that both the rocker 

arm and the wrist plate will be 
plumb when the eccentric occupies 
the central position, as in Fig. 56, 
and marks A B should be made on 
the hub and wrist-plate stud at this 
central position, as shown in Fig. 
57. The eccentric should then be 

riG. 53. — PLUMBING WRIST PLATE AND , , , » ., , ^^• 

ROCKER ARM. turned to one of its extreme posi- 

tions. A temporary mark should be 
made here lightly as at D, Fig. 58. The eccentric should then be turned 
to the opposite position and another mark made at C. The distance from 
5 to C should equal the distance from B to D. If there is any discrepancy 
the reach rod should be lengthened or shortened until the distance which 
the wrist plate travels on each side of the mark B is the same, when the 
rod will be of the proper length. 

Disconnect rod and place the wrist plate in its central position. With 




THE CORLISS STEAM ENGINES 



59 



the wrist plate in this position and both steam valves hooked on, the 
valves should have the proper lap. This may be ascertained by removing 
the steam bonnets and inspecting the marks on the valves and seat made 



J C 



FIG. 57. — CENTRAL MARKS ON 
HUB OF WRIST PLATE. 



11 n 

FIG. 58. — WRIST PLATE IN 
EXTREME POSITION. 



by the builders, as shown in Fig. 59, where F is the working edge of the 
valve, E is the edge of the steam port and the distance E D is the lap 
of the valve. The proper lap to give the valves can be found in the 
accompanying table, and the radial arms should be lengthened or short- 
ened by means of the left- and right-hand thread connections until the 
lap is equalized and of the right amount. 

Then turn the wrist plate to the extreme travel on the head and ad- 




FIG. 59. — SHOWING MARKS 
ON VALVE SEAT. 



FIG. 60. — ADJUSTING CLEARANCE 
AT CATCH BLOCK. 



just the length of the dashpot rod so there will be an equal clearance 
around the catch block, as shown in Fig. 60. Turn the wrist plate to 
the other extreme and adjust the other dashpot rod in the same manner. 



60 VALVE SETTING 

Next with the governor in its lowest running position resting on the 
collar or pin provided for the purpose, turn the wrist plate so as to pick 
up the head-end steam valve and then turn it over until it nearly reaches 
the mark corresponding to its opposite position, and adjust the governor 
rod for the head-end valve so that the trip block E, Fig. 60, just engages 
the inner member of the hook K, making sure that the valve will be re- 
leased when the wrist plate reaches its extreme position. The same 
adjustment should now be made at the crank end of the cylinder. The 
governor should then be blocked up to its highest point of travel, when the 
trip blocks should be in such a position that neither steam valve can be 
lifted by the hook. 

Next put the governor down to its lowest running position and turn 
the engine to the dead center nearest the cylinder. Hook the reach rod 
on the wrist plate and turn the eccentric around in the direction the 
engine is to run until the hook has engaged the head-end steam valve 
and raised it sufficiently to open the port to the amount of the lead as 
shown in the table. Fix the eccentric at this point, then turn the engine 
over in the direction it is to run until the crosshead is at a point deter- 
mined from the column of trial compressions given in the table, and which 
varies from If to 4 ins., according to the size of the engine, and examine 
the crank and exhaust valve. The line indicating the edge of the port 
and edge of the valve should exactly coincide. If they do not, adjust 
the length of the exhaust valve rod as the case requires until the marks 
are together. 

Continue turning the engine until the crank end dead center is reached, 
making sure that the head-end steam valve has been released, and see if 
the crank and valve has been opened to the amount of the lead. If not, 
make any required adjustments in the length of the radial area operating 
the crank and steam valve. Continuing turning the engine until the cross- 
head is within the same distance from the end of the return stroke as in 
the first instance, corresponding to the amount of trial compression, and 
adjust the position of the head and exhaust valve so that the lines will 
coincide, as was done at the opposite end of the cylinder. Make sure that 
the crank-end steam valve is released by the time this stroke is completed, 
and the valves will be properly set, but should, of course, be verified by 
the indicator. This method applies to a single eccentric engine, but the 
same process can be used in the case of the steam valves on double eccen- 
tric engines except that when the wrist plate is in its central position 
and both steam valves are hooked on, the valves should give about one 
fourth port opening on each end instead of lapping, as in the case of a 
single eccentric engine, and very little lap should be allowed when the 
dashpots are down to their extreme positions — only enough, in fact, to 
make the valves steam tierbt. 



THE CORLISS STEAM ENGINES 61 

Centralization of the valve gear is aecoinplishecl in the same manner 
as for single eccentric engines, but the steam and exhaust valves are, of 
course, set separately. When setting the steam eccentric, the style of 
wrist plate operating the steam valves determines whether the eccentric 
should be moved in the same direction as the crank or in the opposite 
direction, when giving the valves lead. In any case, this may be deter- 
mined by an inspection of the stjde of gear employed. In the same man- 
ner, an inspection of the valve gear must be made to determine in which 
direction to turn the eccentric when adjusting the exhaust valves at the 
point of closure or compression. If the exhaust wrist plate is moved by 
an attachment above its point of support, as with the steam valves, the 
eccentric must be moved in the direction in which the engine is to run, 
and the position of the eccentric will be nearly that of the steam eccentric. 
If the point of attachment of the exhaust reach rod is below the point of 
support, the eccentric must be moved in the opposite direction to that in 
which the eno;ine is to run. 



VI 
THE GREENE-WHEELOCK ENGINE 

The Hill valve with Greene cut-off is on all makes of the Greene- 
Wheelock engine of to-day. In the first years of its maintenance this 
engine was installed extensively in Canada, England, France, and Ger- 
many, as well as in this country, where more than one thousand were put 
in service by the original builders. Successive builders have improved the 
type all the while, steadily placing them in service, and to-day thousands 
of these engines are in use in this and foreign countries. For this reason, 
and because this valve gear is interesting to operators, this chapter is writ- 
ten to bring out the principal points to be considered in the setting of the 
valves. 

Each cylinder is equipped with four valves of the Hill grid-iron type, 
two steam and two exhaust to each cylinder, each individual valve being 
driven by a separate eccentric. The valves are arranged , two each in a 
plug, there being one steam and one exhaust in each plug, and one plug at 
each end of the cylinder. 

The best-known advantages of this valve and gear are large port open- 
ings with a minimum of travel, which in connection with the Greene cut-off 
on the steam and the toggle motion on the exhaust valves gives the quickest 
action at the right time to both. A minimum lap is also obtained with the 
aid of the gear, an added reason why it is of first importance to under- 
stand the movements of the valve and gear and to use care in all adjust- 
ments. 

The valve plugs contain the valve seats as an integral part of the plug, 
which are in turn removable for repair, together with the valves when in 
position, and to the plug is attached the head which holds the working 
parts of the valve mechanism. The whole makes a complete removable 
structure, separate from the cylinder, which can be disconnected from the 
eccentrics and removed from the cylinder in a few minutes for inspection, 
repair, or permanent replacement. 

The arrangement of the valves below the cylinder is the Wheelock sys- 
tem. The advantages are short ports, small clearance, together with a 
means of discharge of the water of condensation through the exhaust with- 
out entering the cylinder, and if in extraordinary cases water collects in 

62 



64 



VALVE SETTING 



the cylinder it is relieved by the raising of the inlet or steam valve from 
its seat. 

General Arrangement of Valve Gear 

The general arrangement of the valve gear, eccentrics, etc., can be seen 
by reference to Fig. 61, which is the high-pressure side of a cross-com- 
pound engine. The eccentric shaft A being geared to the main shaft of 
the engines at a makes it positive in action. The eccentrics which actuate 
the valves are at B, C, D, and E. These eccentrics are secured to the shaft 

by a friction key, which is hidden by 
a plate on the side of the eccentric, 





FIG. 62. 



FIG. 63. 



secured in place by screws. The eccentrics C and D are the steam eccen- 
trics and B and E the exhaust. They are attached to the valve mechanism 
by their respective rods. The throttle of the engine at F admits steam 
to the steam chest under the cylinder and equally to the valve plugs G 
and H. 

An understanding of the valve plugs and their location may be had by 
reference to Figs. 62, 63, and 64. Fig. 62 shows a longitudinal section 
of the cylinder and the cross section of the valve plug at A. This view 
gives the location of the inlet (steam) valve and seat at a and the outlet 
(exhaust) valve and seat at h, the steam chest B B forming a jacket for 
part of the cylinder, as well as admitting the steam through the inlet a 
into the cylinder. From the cylinder the steam passes out through the 
outlet & into the exhaust passage 0. 



THE GREENE-WHEELOCK ENGINE 



65 



Fig. ()3 is a cross section of the cylinder through the clearance space 
and a longitudinal of the valve plug in that end of the cylinder, showing 
the back of the inlet valve seat, with the outlet valve cut away. 

Fig. 6-J: is a view of the valve plug with all the parts assembled. This 
view shows the inlet- or steam-valve side of the plug. The inlet valve is 
at a; the spring which holds it to its seat when not under steam pressure 
is at h; and c is the pusher crank which actuates the valve by means 
of a cam at d, which comes in contact with the latch of the valve-stem 
head e. This is fastened to the inlet valve-stem by clamp bolts. The 
inlet valve-stem screws into the nut /, so that by loosening the clamp bolts 




FIG. 64 



of the head e and turning the rod, an adjustment of the valve setting can 
be made, as will be shown later. 

The inlet valve is opened by the pusher cam pushing it forward, but 
is released from this cam through the means of a trip cam on the bottom 
of the valve-plug head, which is connected to the governor rods. When 
released by the trip cam, the valve cuts off by means of the steam pressure 
on the valve stem controlled by a daslipot arrangement in the valve-plug 
head, to which the other end of the rod is attached. 

The outlet valve is inside of the valve plug under the strut g. The 
position of this valve in relation to the inlet can be noted by reference 
to Fig. 62, where the cross section of the valves and seats is shown. The 
outlet valve is actuated by the eccentric acting on the toggle joint li, con- 
nected between the two pairs of links, from the point i. where it is fixed, 
and the point /, where the link is fastened to the valve-rod head h on the 
outlet valve stem. 



66 



VALVE SETTING 



Position of Valves iisr the Plugs 

A more thorough understanding of these valves may be obtained if the 
position of the valve inside the plug (in relation to the position of the 
eccentric and other mechanism) is known. 




FIG. 65. 



For the sake of simplicitj'-, each valve, i.e., outlet and inlet, is shown 
with its gear separate for the moment, eliminating one while the other is 
under consideration. The cross section of the valve and seat is not in 



THE GREENE-WHEELOCK ENGINE 



67 



proper relative position, but so placed in these figures as to best show the 
positions at given points of the eccentric travel. 

Fig. 65 represents the inlet (steam) valve and mechanism asseml>led. 
The scale is for a size these makers build for cylinders under 16 in. in 
diameter, or their " size A " valve. It shows the valve lapped at the inner 
end of its travel, with the eccentric at the top center of its travel. 

Eeferring to the illustration, then, A A is the center line of the eccen- 
tric shaft, B B is the center line of the eccentric rod, C C is the center of 




FIG. 66. 



the pusher crank at the top of its movement, D D is, the pusher-crank 
center at the lower end of its travel, E E is the center line of the pusher- 
crank shaft, F F is the line of travel of the pusher-plate edge, G G is the 
line of travel of the pusher-crank pin, a is the pusher, h is the latch, c is 
the pusher crank, d is the valve, e is the valve seat, / is the lifter, g is the 
trip cam, li is the trip-cam yoke, i is the valve stem and ;" is the head. 



68 VALVE SETTING 

It will be noticed that the pusher a just engages the edge of the plate 
on the latch h, with the pusher crank c at the top end of its travel and the 
eccentric the same. Whenever the eccentric, pusher crank, and pusher are 
in the position here shown, the valve d should be lapped over the ports of 
the valve seat e as shown. 

When the latch 1) and the pusher a just engage at the point shown, the 
lifter / is raised by the trip cam g to the highest working position, and the 
valve will not open. In order to open full port, the lifter must lower the 
latch so that its bottom edge will be along the line H TI and the pusher 
plate can engage it up to the point X, where it will have the valve open 
full port, as sho^vn in Fig. 66, which shows the essential parts to note of the 
same gear as in Fig. 65. The same letters are used to denote the same 
parts as in Fig. 65. 

By reference to the eccentric circle it will be noted that the eccentric 
is at E, or the bottom of its travel, and the pusher crank the same. The 
latch h has been allowed to fall to the position along the line F F in Fig. 
65, and so the pusher has moved everything along to the outside end of the 
valve travel where the ports are full open and the valve is on the point of 
being released to cut-off. 

Fig. 67 is a detail of the trip cam g (Fig. 65). This cam is connected 
to the governor rod at A and pivots on its pin at B in the cam yoke. When 
the governor is on its stop before coming up to speed the roller of the lifter 
is as shown for " full stroke " and the valve will be carried in full-port 
opening, as in Fig. 66, before releasing for cut-off. After the engine is up 
to speed and the governor lifted from its stop, the cam will be moved along 
in the direction that will bring the lifter roller at any point up to that 
shown for " short cut-off." When the roller reaches there, the valve is 
traveling only enough to overcome the lap. If the engine slows down and 
the stop is not set, the governor will go low enough to throw the trip cam 
over so that the lifter roller is up to " safety," when the valve will not 
travel at all, the latch being lifted so high it will not come in contact with 
the pusher plate, as in Fig. 65. 

A mark is put in the edge of the flange of the trip cam, as at C, Fig. 67, 
and this mark should come under the center of the lifter roller, as shown, 
when ready to start up or carry full stroke. (jSTote the rules for adjust- 
ment given later.) 

Fig. 68 shows the outlet (exhaust) valve and plug with the valve gear 
assembled. This first view shows the valve wide open to ports on the out- 
side end of its movement. It will be noted that the eccentric is on the 
bottom center of its travel and the toggle stub end a is at the lowest point 
it reaches below the line C C, and the outlet valve-stem head center 6 has 
reached its farthest point of travel toward the valve plug. 

In Fig. 69 the eccentric has reached E on the eccentric circle and the 



THE GREENE-WHEELOCK ENGINE 



69 




70 



VALVE SETTING 



toggle stub end has come up toward the line C C ; the point h has reached 
a position corresponding to the near edge of the ports and the valve has 
just cut off or closed for compression. 

In Fig. 70 the eccentric has reached the point E on its travel, and the 
toggle links now forming a straight line from the end of one to the end of 




FIG. 69. 



the other, the valve is lapped as shown with the point h where it is. This 
is the extreme of travel for the valve and stem in this direction. 

In Fig. 71 the eccentric has reached the point E, the top center of its 
travel, and the toggle stub end the same, but the point b has come back on 
its travel, as well as the valve, until they nearly open again. The eccentric 



THE GREENE-WHEELOCK ENGINE 



71 



continuiiig until it reaches E' , in Fig. 70, the point h and the valve will 
have again lapped, and continuing until it reaches E', Fig. G9, the valve 
will have come back to the position shown, or is on the point of release. 




FIG. 70. 



It will be seen by this that the valve moves four times between the 
points of closure and opening, which is a distinctive feature of this valve. 



72 



VALVE SETTING 



Conditions to be Avoided 

There are some general conditions which if they existed on this valve 
gear would cause trouble, and it is well to speak of these. If the inlet 




FIG. 71. 



eccentric rod is too long, the valve-stem latch and pusher may not engage, 
or if they do, the action may be too early. If the rod is too short, it will 
cause late action. 

If the outlet eccentric rod is too long it will cause the valve to open too 
quickly, and running back too far will partially obstruct the ports and it 



THE GREENE-WHEELOCK ENGINE 73 

will close late. If too short, the opening will be late and the closure early, 
with a reopening on the back travel. 

The eccentrics in these illustrations run in the direction of the arrows, 
but also run opposite to suit the conditions, any change of the position 
of the eccentric on its shaft has the same effect as though the eccentric 
were on the main shaft. 

Instructions for Proper Setting 

The following instructions are from the builders of these engines, and 
if adhered to will give proper setting of the valves. The preceding illus- 
trations Avill aid to a full understanding of these operations. 

For reference and a means of checking off the action of the valves it is 
stated that " A-size " valves have i^-i'o.. lap, with f in. travel, and are 
generally used on cylinders up to and including 16 ins. in diameter; 
'' B-size " valves have Te'ii"^- ^^V> with 1^-in. travel, and are generally used 
on cylinders from 18 to 26 ins. in diameter, inclusive; "C-size" valves 
have ^-in. lap, with If -in. travel, and are used on cylinders from 28 ins. 
in diameter u]3ward. 

When starting to adjust the valves, first have all eccentrics loose on the 
cylinder shaft, and, second, determine the direction the cylinder shaft is 
to run, and always rotate the eccentrics in the same direction, whether 
loose on the shaft, or when the shaft and eccentrics turn together. 

To Adjust the Travel of the Steam Valves 

On the edge of the pusher crank (Fig. 72) a line is made in the shop, 
and on the side of the plug head, next to the pusher crank, a correspond- 
ing line is made (where the arrow points). When the line on the pusher 
crank corresponds exactly with the line on the side of the plug head, the 
pusher plate is vertical, as in Fig. 65. This is its most backward position. 

Adjust the eccentric rod for this valve to such a length that in turning 
the eccentric around on the shaft the line on the edge of the pusher crank 
comes back to correspond exactly with the line on the plug head at each 
revolution. Then, by shimming, adjust the bridge-supporting trip cam 
(shim where the arrows in Fig. 73 denote), so that the steam valve will 
travel f of an inch on " A size," 1^ ins. on " B size," and If ins. on 
"^^ C size," but bear in mind that the valve must trip at the end of its 
travel and the bridge must not be so low that the valve will carry the full 
stroke without tripping. The roller of the lifter must be in position for 
full travel, as shown in Fig. 67. 



74 



VALVE SETTING 



To Set the Steam Valves 

On the steam-valve stem four scratch lines are made. These lines 
represent the valve on its lap, the valve just opening, the valve wide open, 
and the valve pushed in until it strikes the plug. With each valve gear a 
steel- wire tram (a, Fig. 74)- is sent. Just ahove the valve stem on the 
plug-head casting a prick-punch mark will be found. Loosen up the inlet 
stem head (;, Fig. 65) on the stem, then shove the valve back until it 
strikes the plug. If the valve is set correctly, the tram with one end in 
the mark on the plug-head casting, as shown in Fig. 74, should with the 
other end meet the tirst scratch line on the valve stem (nearest the out- 
side end of stem). If the point of the tram does not coincide with this 





FIG. 72. 



FIG. 73. 




^o^ 



\^ .Tram 



FIG. 74. 



FIG. 75. 



line, the valve stem should be screwed in or out until it does. The valve 
should then be let back so that the dasher strikes the head, and the inlet 
stem head be brought back against the pusher plate when the pusher plate 
is vertical, as in Fig. 65, leaving -eV-in. clearance between the pusher 
and latch plates. It will then be found that the point of the tram will 
correspond with the fourth mark on the stem, with the valve closed, as in 
Fig. 65. 

When the valve is moved forward so that the tram point corresponds 
with the third line on the stem, the valve is just closing or opening, and 
when moved farther so that it corresponds with the second line, the valve 
is wide open. The travel of the valve should be between the second, third. 



THE GREENE-WHEELOCK ENGINE 75 

and fourth points spoken of, and it should trip just as the tram point cor- 
responds with the second line from the outside end. Then, with the piston 
on dead center, the eccentric should be revolved on the shaft to bring the 
steam valve -3^2 of an inch open on the crank end and e\ of an inch on 
the head end. The eccentric should then be clamped to the shaft, and the 
valve is set. 

To Adjust the Exhaust Valves 

On the outside of the plug head, where the arrow points in Fig. 75, 
are four prick-punch marks. On the outside of the outlet stem head where 
the tram rests is another prick-punch mark. This is for one point of 
tram. 

To Adjust Valves for Lap 

The eccentric rod should be disconnected from the eccentric. Shove 
the valve back as far as it will go. With the valve in this position, the 
outside end of the tram should fall into the fourth mark on outside of the 
plug head nearest the cylinder. If it does not, loosen up the nut holding 
the outlet stem head, and screw the stem in or out sufficiently to make the 
tram come up into the fourth mark. Then tighten up the nut holding the 
outlet stem head, connect the eccentric rod to the eccentric, lengthen or 
shorten this eccentric rod so that the travel of the valve due to one revolu- 
tion of the eccentric will move the tram from the first to the third prick- 
punch mark, and no farther. 

The eccentric should then be set so that when the piston is about 5 
ins. from the end of the return stroke, the exhaust valve should have 
just closed, as in Fig. 69, and the tram point would fall into the second 
mark on the plug head. 

As these valves must be set while the valves are out of sight, a strict 
adherence to these rules of adjustment must be followed, care being taken 
to be accurate, but Figs. 65, 66, 67, 68, 69, 70, and 71 will help to a 
clear understanding of what is done in this adjustment and subsequent 
operation. 



VII 

THE BROW^T ENGINE 

The engine is provided with two steam valves and two exhaust valves 
of the flat multiported type, each set being operated by a separate eccen- 
tric and all independently adjustable. The steam valves are placed on the 




FIG. 76. 



side of the cylinder and the exhaust at the bottom, the latter affording 

an ideal water drain, as shown in Fig. 76, which is a section through 

the valves and cylinder. The operation of the steam valves can best be 

76 



THE BROWN ENGINE 



77 



seen by referring to Fig, 77, which shows the position occupied by the 
parts at the commencement of the piston stroke. The eccentric is con- 
nected to the steam lever B, on the lower arm of which is the steel lifting 
block A which has just engaged the latch C. This is journaled on a pin 
on the guide D of the steam-valve stem. 

It is evident that if the eccentric draws the arm B toward the crank 
shaft the block A will be raised and carry with it the latch and guide, 
causing the valve to open. This upward movement continues until the 




FIG. 77. 

tail of the latch comes into contact with the trip lever E, which causes 
the latch to release the block and allows the valve, with the stem and 
guide, to fall to their initial position, thus cutting off suddenly the admis- 
sion of steam. A steam pressure equal to that on an area equal to the 
valve stem also assists to close the valve, whose fall is cushioned by the 
dashpot F, the amount of cushion being regulated by the cock H. The 
trip lever E is carried by the trip shaft G, which is connected to and 
actuated by the governor. 

The action of the exhaust is shown in the plan view. Fig. 78. The 
exhaust sliding bar A is actuated by the eccentric and is connected by 



78 



VALVE SETTING 



the link B and the lever C to the exhaust-valve stem guide D, which is 
connected to the valve by the stem E. The manner of transferring the 
motion of A to the valve is quite apparent, but it should be noticed that 

the arrangement gives the greatest 



velocity of valve movement at the 
points of opening and closing 
and provides a long dwell between 
these points. 

The governor now provided 
with these engines is of the type 
shown in Figs. 79 and 80, the first 
showing the construction of the 
governor and the second its rela- 
tion to the trip shaft and other 
parts of the engine. 

The centrifugal action of the 
two weights A and B, Fig. 79, is resisted by the springs, but their out- 
ward motion rotates the sleeve C, which has a diagonal slot in which is 
fitted a roller D on a pin fast to the central stem E. The central 




FIG. 78. 




FIG. 79. 



stem is by this action forced to the left in the direction of its length, 
and this moves the double lever F to which the stem is connected out- 



THE BROWN ENGINE 



79 



side the governor case. The connection of the doul^le lover F to the 
trip shaft is shown in Fig. 80, in which is also shown the connection 
to the dashjDot, and a stop, with the handle in a vertical position, for 
checking the ont\\'ard motion of the stem. From the description of the 
action of the steam-valve gear, it is evident that a rotation of the trip 
shaft causes the trip lever E, Fig. 77, to release the latch earlier or 
later in the stroke, according to the load, and so vary the point of cut-off. 
An extra movement of -^ in, of the stem beyond its extreme governing 




FIG. 80. 



position operates a safety stop which does not allow the latch to engage 
the lifting block and causes the steam valve to remain seated and so shut 
ofE steam completely. Its mode of operation will be apparent from what 
follows. 

It is seen that this gear has the quick opening and release features, 
and the use of separate eccentrics for the steam and exhaust valves allows 
separate adjustment for each and permits of a wide range of cut-off and 
compression. The directions for setting the valves may be stated as 
follows : 

The first requisite is the proper adjustment of the four valve stems 
to secure the necessary lap on each valve. 

Beginning with the steam valves, remove the guide box A, Fig. 81, 



80 



VALVE SETTING 



and on the valve-gear bracket a scratch mark B, prick-punched at each 
end will be found. Now disconnect the dashpot connections from' the 
steam-valve stem guide D and allow the valve to drop as far as it will 
go, and then adjust by turning the valve stem in or out of the valve nut 
until the distance between the scratch mark B on the valve-gear bracket 

and the bottom of the brass drip 
cup G is the exact width of a steel 
gauge, or ^ in. Then make the 
stem fast to the guide by means of 
the nuts at E. 

The dashpot stem G should then 
be adjusted until the top prick- 
punched scratch mark on the guide 
D just shows above the top of the 
guide box. Tighten the nut on the 
dashpot stem. Make these adjust- 
ments on both steam valves. Now 
turn the full side of the steam 
eccentric on the forward or dead 
center farthest from the cylinder, 
having first seen that the dashpot 
on the crank-end steam valve is 
properly seated. When the eccen- 
tric occupies the dead center, the 
lifting block A, Fig. 77, on the 
crank end should then have just 
engaged the latch, with perhaps -3V- 
in, clearance. If this is not the 
case, the eccentric rod should be 
adjusted until this clearance is ob- 
tained. When the eccentric occu- 
pies the dead center nearest the 
cylinder, see that the foregoing conditions are fulfilled at the head or 
end of the cylinder farthest from the crank shaft. If such is not 
the case, adjustment must be made by the right and left rod connect- 
ing ■ the two steam levers until the proper clearance is obtained on the 
head end. 

Now have the eccentric turned around on the shaft and see that both 
valves are alternately raised an equal distance, which will be the case if 
the adjustments have been properly made. 

Place the crank and the full side of the eccentric on the dead center 
nearest the cylinder. The lifting block should have now just engaged the 
latch on th-e head end. Have the eccentric turned around on the shaft 




FIG. 81. 



THE BROWN ENGINE 81 

in* the direction in which the engine is to run until the valve opens the 
ports the amount of the lead, which should not exceed -^ in., unless it is 
positively known that the engine will run better with more lead. Have 
"the eccentric fixed to the shaft at this point. The amount of lead may 
be accurately determined by removing the upper head of the valve chests 
and measuring the lead by means of pieces of thin steel -g-j in. thick. 
The end of the steel strip is to be placed against the valve seat while the 
eccentric is being slowly turned around on the shaft. As soon as the 
strip enters the port the valve will have opened -^ in. 

Have the crank turned, in the direction it is to run, to the opposite 
dead center or crank end. 

The opposite steam valve should now have opened the port the amount 
of the lead, which it will do provided the work of equalizing the move- 
ments of the valves has. been properly done. If the lead is found to be 
correct, the eccentric must then be permanently fixed in the position in 
which it will now be found on the shaft. 

The movement of the exhaust valves is now to be equalized in the 
same manner as for the steam valves. Marks will be found on the ex- 
haust-valve stem guide D and guide box F, Fig. 78, showing the position 
of the valves, or should the marks have become obliterated, the valves 
may be seen by removing the valve-chest bonnets, and by the aid of pieces 
of thin steel their exact location may be determined, the same as with 
the steam valves. 

To determine the proper length of the exhaust-valve stem, draw the 
valve forward until it strikes. Screw the valve stem into the valve nut 
until the marks H and I come together, then make the nut fast at L. 
The lines J and K show the lap of the valve. G and J when together 
show the opening line. 

To set the exhaust valves, mark the guides on the frame at each end, 
varying from 2^ ins. for the small engines to 3 or 3^ ins. for the larger 
ones, from the full stroke of the crosshead. Then have the crank turned 
in the direction the engine is to run until the crosshead reaches one of 
these marks. 

Assume that the exhaust eccentric is on the dead center nearest the 
cylinder and that the crosshead has reached the line on the guides nearest 
the cylinder. The exhaust eccentric is now to be turned around on the 
shaft in the direction the engine is to run until the exhaust valve on the 
head end just closes the port or until the lines G and J come together. 
Fix the exhaust eccentric to the shaft at this point. Then have the crank 
turned in the direction it is to run until the crosshead reaches the line 
at the opposite end of the guides, when the exhaust valve at that end of 
the cylinder should have just closed the port also. 

If it does, the compression will then commence when the piston reaches 



82 VALVE SETTING 

a point from the end of the stroke corresponding to the distance marked 
on the frame guides. 

The proper amount of compression and lead will have to be finally 
determined by an indicator after the engine has been started and run 
under working conditions. This is recommended in every case. 

If an engine is to be run condensing, it will require more compression 
than an engine running noncondensing. 

After both sets of valves have been properly adjusted attention should 
be given the governor. 

Looseji the governor springs until the weights can be readily moved 
from one position to the other by means of the central stem. Kow press 
the stem in until the weights are in their outer position, and block them. 
Loosen the set screw in the governor connection lever on trip shaft and 
move the trip lever^ E, Fig. 77, nearest the governor, which is permanently 
fastened to the trip shaft, either toward or away from the latch as the case 
may require, until the crank-end steam valve upon being raised will cut off 
when the second prick-punched scratch mark on the guide D, Fig. 81, 
appears at the to^^ of guide box. Then tighten the set screw in the gover- 
nor lever on the trip shaft. That is, with the governor weights in their 
outer position, the steam valve is only allowed to lift enough to just un- 
cover the lap. The lap is the distance between the first and second scratch 
marks. 

Place the small handle on the front of governor in a vertical position 
and pull the stem out until it is stopped by the handle, which will bring 
the governor weights to their inner position. The steam valve now being 
raised should not be cut off until the third prick-punched scratch mark 
shows at the top of the guide box, or -^ in. less than the full throw of 
the short horizontal arm of the steam lever B. The movements of the 
two steam valves may now be equalized by means of the taper pin L, in 
the trip lever of the head-end steam valve. This can be seen in Fig. 77, 
and acts as a taper key. By loosening the set screw and driving the pin 
in, the cut-off is shortened; by driving it out, the cut-off is lengthened. 

The taper pin is not used with the latest design, the movements of 
the two valves being equalized by means of the two knurled finger screws 
on the yoke made fast to the trip shaft at the head-end trip lever, which is 
itself loose on the trip shaft. 

In setting the safety stop, proceed as follows : With the small safety 
stop handle in a horizontal position and the central stem pulled out as 
far as it will go, the governor balls are allowed to reach an extreme point 
beyond their inner governing position, which imparts to the central stem 
an extra -jV-in. motion beyond its working limit. Block the governor in 
this position. Now screw J, Fig. 77, in until the lower end of the pawl 
E strikes the tail of the latch C, and the steel on upper end of this latch 



THE BROWN ENGINE 83 

is just thrown out of engagement with the lifting block A. Make the 
check nut tight on the screw J. 

This adjustment being made on both ends of the cylinder, each valvo 
should be raised two or three times to see that proper clearance has been 
given between the steel on the latch and the lifting block, so that the 
latch cannot hook on at this point. 

Thus, should the governor belt break, or by any other cause the gov- 
ernor balls be allowed to reach their extreme inner position, the steam 
valves remain seated, cutting off any further supply of steam to the 
cylinder. 

After setting the valves and safety stop, the small handle on governor 
should be moved to the horizontal position and left there until such time 
as further valve setting is necessary. In that position the safety stop is 
in operation at all times. Of course, after shutting down this will block the 
steam valves from lifting and prevent starting up until some change is made 
in the position of governor balls or other parts. All that is necessary is to 
loosen the small binding handle on governor link and turn the pin, which 
is eccentric in the link, half around, in which position the trip levers are 
given -J in. advance ahead of the governor. After starting up and nearly 
reaching speed, turn eccentric pin to original position and lock it. 



VIII 

THE Mcintosh & seymoue engine 

The valves of this engine are of the multiportecl flat gridiron type, 
located at the four corners of each cylinder in much the same fashion 
as the Corliss. There are two main steam valves and two main exhaust 
valves, in addition to which there are two riding cut-off or auxiliary 
valves placed on top of the main steam valves. The valves are all 
driven by positive valve gear, consisting of plain links and rockers, 
operating with a toggle motion, and their movement is crosswise of the 
cylinder bore. 

Figs. 82, 83, 84, and 85 show in outline the arrangement of the valves 
and gear on a horizontal engine. The main valves, both steam and ex- 
haust, are driven by an oscillating shaft M, which derives its motion by 
a rocker R and link L from a fixed eccentric F on the engine shaft, as 
shown by Fig. 83. This gives fixed points of opening and closing, and 
governs the admission of steam and the opening and closing of the ex- 
haust. The connection between the shaft M and the main steam and 
exhaust valves is shown in the cross section, Fig. 84, and it will be seen 
that these main valves can be adjusted to vary independently the admis- 
sion, the release, or the compression. In practice the main steam valve 
is set to close when about 60 per cent, or more of the stroke has been 
completed, so that steam may be carried up to this point unless cut off 
earlier by the auxiliary valve. The governor operates only these auxiliary 
or cut-off valves. This is done through the medium of the lower rock 
shaft A and the arrangement of links and bent lever, as shown in Fig. 
85. The shaft A is driven from the governor eccentric G by means of 
the bell crank B and link I. The governor eccentric is arranged to revolve 
around the shaft by the action of the governor, as shovm in Fig. 82, in- 
stead of across the shaft, as is more common in shaft governors. It thus 
governs by varying the angular advance of the eccentric in place of chang- 
ing the travel of the valve. The arrangement is such that when cut-off 
takes place the cut-off valve is moving in an opposite direction to the 
main steam valve, giving a very rapid closing of the port and, conse- 
quently, the desired sharp corner on the diagram. 

As the valves are multiported, only a very small movement is required 

84 



THE McINTOSH & SEYMOUR ENGINE 



85 







86 



VALVE SETTING 



to give full port opening. This varies from ^ in. to 1^ ins. from the 
smallest to the largest size of cylinder. 

Figs. 86 and 87 show enlarged views of the cylinder and valve gear. 




FIG. 86. — DETAILS OF GEAR. 



and in connection with Figs. 76 and 77 will allow a ready understanding 
of the valve motion, (The detailed views are stripped as far as possible 
of unnecessary details, such as nuts, housings, oil cups, keys, etc.) The 




FIG. 87. — DETAILS OF GEAR. 



stroke motion derived from an eccentric or any other crank is of course 
more rapid at the center of the travel than at the ends, and advantage is 



THE McINTOSH & SEYMOUR ENGINE 



87 



l^y^^^ww^ 



i.\vxxv\v^ 




rCUTOFF VALVE 
-MAIN STEAM VALVE 



■z^///y///y////y///////y/y///yy'///,^yA 



^ssss\s^v| 



taken of this fact to distort the motion received from the eccentric so as 
to secure a rapid movement at one end of the valve stroke and to retard 
the motion at the other end of the stroke. This is done by arranging 
the oscillating movement of shafts M and A by means of the rockers and 
links from the eccentrics, so that the pins P P, Fig. 86, and p p, Fig. 87, 
will move slightly past the center at the extreme of the stroke, as shown 
by the dotted lines indicating the angular movement. The result is that 
at one extreme of the travel pins P and f are moving through the flat 
part of the arc and give a large horizontal movement for a small angular 
motion; while at the other extreme the pins move through a consideral)le 
angle without much in-anJ-out motion. This is conveyed to the valves 
by the gear in such manner that 
the valves open and close quickly, 
but remain practically still when 
closed. 

The greater part of the valve 
movement takes place when the 
valve is open, and at such times 
the valve is partially balanced or 
relieved of the steam pressure. 
Consider, for instance, the cut-off 
valve. It will be closed by the ac- 
tion of the governor at, say, from 
20 to 30 per cent, of the stroke, 
while the main steam valve, upon 
which it seats, will remain open 
much longer. As soon as the 
edges of the bridges of the cut-off 
valve project over the ports of the m.ain valve the cylinder pressure will 
balance it by the amount of the projection, and this balancing will increase 
as the cut-off bridges cover the main ports. The main steam valve will be 
similarly balanced between the cylinder and the cut-off valve when it closes, 
and the exhaust valve moves under very little pressure at any time. 

On compound or triple engines the same valve arrangement is used 
on each cylinder, the main valves being driven by a fixed eccentric, while 
all the cut-off valves are driven by the governor eccentric, thus equalizing 
the Avork on the various cylinders. 

The main rock shafts Jf and A are carried on brackets from the lower 
part of the cylinder, and the short upper pins or shafts m and a are car- 
ried by similar brackets at the upper corners of the cylinder. 

Adjustment is provided at all wearing points, the links having bronze 
boxes with key take-up (not shoAvn in Figs. 86 and 87), and the rock 
shafts having regular babbitted and capped bearings. The valves and the 




EXHAUST VALVE 



^///////////////////////////////A 



y/////////////////////////////^7^7^ 



FIG. 88. 



§8 VALVE SETTING 

crossheads c c, Fig. 86, are arranged to wipe over and all valve stems are 
adjustable. 

The valve seats or grids are separate from the cylinder and are put 
in place with scraped joints, avoiding the use of soft packing. Valve cov- 
ers are provided over each of the four sets of valves, as in Fig. 88. 

As shown in Figs. 86, 87, and 88, the ports and clearance spaces are 
very small, the total clearance in most cases being less than in the Cor- 
liss type. In a word, the distinctive features of this valve gear are : Grid- 
iron valves at four points; the main valves driven by a fixed eccentric 
and controlling admission, release, and compression; and the cut-off valves 
driven by a governor eccentric, controlling cut-off by varying the angular 



TRAVEL 

^" I ^MAIN STEAM VALVE 




FIG. 89. — MAIN STEAM VALVE IN EXTREME INNER POSITION. AUXILIARY STEAM 
VALVE IN CENTRAL POSITION. 

advance; all driven by a positive valve gear which permits of high rotative 
speeds and dispenses with dashpots and releasing gear. 

Figs. 89 and 90 are enlarged views of the valves and grids, and show 
the shape of valves and ports, the laps and the attachment of valve stems; 




-EXHAUST GRID 

FIG. 90. — EXHAUST VALVE IN EXTREME INNER POSITION. 



while Figs. 91, 92, and 93, in connection with Figs. 83, 83, 84, and 85, 
illustrate the instructions for setting the valves. 



Setting the Valves 

As a .preliminary to setting the valves it is necessary to know the 
strokes, laps, and leads of all valves, the points of cut-off for both main 
and auxiliary valves and the point of exhaust closure or compression. 



THE McINTOSH & SEYMOUR ENGINE 89 

These vary with the individual engine and must be obtained from the 
maker in each case. The strokes, laps, and leads will be given in inches, 
and the points of cut-oft' and compression will be given either in fractions 
of the stroke or in inches of the stroke measured from the dead-center 
point. Having these figures, the first operation is to set the main valves, 
both exhaust and steam. First turn the engine over slowly and by means 
of link L, connecting the rocker E and shaft M, Fig. 83, adjust the angu- 
lar movement of shaft M until the exhaust valve shows exactly the proper 
stroke or travel. A mark will be found completely encircling the valve 
stems at some point outside the stuffing box, as at X, Fig. 91; and the 
stroke can be measured by means of this mark, either from the face of 
the box or from any other fixed point. As soon as the stroke is fixed, 
set up the lock nuts on link L to prevent change, and by means of link 
8, Fig. 64 or QQ, adjust the stroke of the main steam valves. The stroke 
of the exhaust valve is adjusted first because it is directly connected to 
shaft M by links of fixed length, and the correct movement of shaft M 
is obtained without introducing link 8. 

So far no attention has been paid to laps or leads, the strokes only 
being adjusted. Next, remove the valve covers and screw the valve stems 
in or out of the small crossheads c c, Figs. 64 and 66, until the valves 
show the proper lap. 

Then place the engine on the head-end dead center, and roll the fixed 
eccentric F, Fig. 63, around the shaft until the head-end main steam 
valve shows the proper lead or is " line and line," if there is no lead. 
Then lock the eccentric in place by the set screws. 

Before going any further it is well to make a mark on crosshead and 
guides, showing the head-end dead center, as in Fig. 93; its use will be 
explained later. When this is done, roll the engine over to the crank- 
end dead center, and if the work has been accurately done the crank-end 
main steam valve will show the proper lead. Make another mark on the 
guides opposite the mark on the crosshead; the distance between this mark 
and the one formerly made will be the stroke in inches, as shown by 
Fig. 92. 

Now measure forward on the guides, from the head-end dead center, 
a distance in inches equal to the point of cut-off of main steam valve and 
make a mark B. (This distance is given in inches by the engine builder.) 
Place the engine on the forward stroke until the mark on the crosshead 
coincides Math line R, as in Fig. 92, the head-end steam valve should 
come line and line with the port. 

Measure forward again from the head-end dead center to the point of 
compression or closure of the exhaust valve, and make another mark 
on the guides. When the engine is placed on the forward stroke so that 
the crosshead mark coincides with mark 0, the crank-end exhaust valve 



90 



VALVE SETTING 



\ 




i< 






\ 


<„ 


r ' 


^ 


f . 


V, . 


J 


\ 



1 1 


















X 


^' 


o 


o 




1 1 





THE McINTOSH & SEYMOUR ENGINE 91 

should come line and line. Make similar marks r and o on the guides, 
measuring back from the crank-end dead center, for the points of main 
valve cut-off and compression on the return stroke, as shown above Fig. 
92, and by placing the engine on the return stroke, check to see that the 
other valves come line and line. On all main steam- and exhaust-valve 
stems will be found an encircling mark like that at X, Fig. 91. This 
trams, by a tram of known length, with a mark on the cylinder casing 
when the valves are line and line, thus making it unnecessary to remove 
the valve covers. 

The auxiliary or cut-off valves yet remain to be set. Measure forward 
on the guides and locate point Q, the point of cut-off of the auxiliary 
valve as furnished by the builders; also measure back from the crank- 
end center and locate the similar point q for the return stroke. Adjust 
link I, Fig. 82, and link 7i , Fig. 85, to give the proper stroke of the valve, 
measuring the stroke as before by the mark x on the stem. Then turn 
the engine forward until the crosshead mark coincides with mark Q and 
set the head-end auxiliary valve line and line with the port of the main 
valve. Put the engine on the return stroke to point q and set the crank- 
end auxiliary valve line and line with the main valve, the governor remain- 
maining closed during both operations. 

This completes the valve setting. To facilitate future settings, two 
punch marks can be made in the rim of the detaching gear of shaft M 
to agree with a tram from the cylinder face, as in Fig. 93, thus estab- 
lishing at a convenient point the proper angular motion for the stroke 
of the main valves. It is of course necessary to have all shaft bearings, 
links, rockers, etc., in good, snug working order and free from unnecessary 
lost motion. In placing the engine on the dead centers and in turning 
it over to the several points of the stroke, it is equally necessary to take up 
all " play " or lost motion in the direction of rotation, as would occur if 
the engine were actually turning over under pressure. 



IX 



THE BUCKEYE ENGINE 



The Standard Buckeye engine is of the two-valve type, having a bal- 
anced box main valve working over a port at each end of the cylinder, 



CUT-OFF VALVE 



SKELETON DIAGRAMOF VALVES AND GEAR 



rn: 



T 









:? 



to 




ELEVATfON 

FIG. 94. 




PLAN 



FIG. 95. 



and a flat cut-off or auxiliary valve riding inside of the main valve. The 
single short port at each end of the cylinder serves alternately for the pur- 
poses of admission and exhaust. 

92 



THE BUCKEYE ENGINE 



93 



Both valves are driven by positive valve gear. The main valve re- 
ceives its motion from a fixed eccentric and governs the admission and the 
release or compression. The cut-off valve is controlled from the governor 
eccentric and governs the cut-off only. 

The elevation and plan of Figs. 94 and 95, and the sections of Figs. 
96, 97, 98, and 99, show the arrangement and operation of the valves 




STEAM CHAMBER 



FIG. 96. — HORIZONTAL SECTION. 



and valve gear. As shown by Figs. 96 and 98, the valve chest is divided 
by partitions into two separate and distinct parts, a steam chamber and 
an exhaust chamber. The main valve is a flat hollow box of the horizontal 
and vertical sections shown in Figs. 96 and 99, set upright in the exhaust 




FIG. 97. —VERTICAL SECTION A-B. 



chamber and working lengthwise of the cylinder. It takes steam into the 
interior through the four balance pistons B, which connect it with the 



94 



VALVE SETTING 



steam chamber and serve to hold it in place; and steam is admitted to 
the cylinder through ports p, which coincide at proper intervals with the 
cylinder ports P. The exhaust passes out over the ends of the valve di- 
rectly into the exhaust chamber which surrounds the valve. 

In Fig. 96 the engine is on the head-end center and the course of the 
steam and exhaust is shown by the arrows. The main valve is hollow 



0'MMMWM>»W/JMMJJMMMW»mmM>»/W)»WfMWMW///mM^^^^ 



l„„„„„„„,„„„„„„„„„„ 




r\ 



STEAM CHAMBER 



EXHAUST CHAMBER 



FIG. 98. —VERTICAL SECTION C-D. 




and supplies its steam from the inside; its motion is just opposite to the 
piston movement, and its eccentric follows the crank instead of leading 
it, as shown in the skeleton diagram of Fig. 94. The balance pistons B 
are packed in their bores by spring rings, and have a scraped joint on the 
back of the valve; this makes a steam-tight passage from steam inlet to 
cylinder, irrespective of the remainder of the valve chest. 

On the side of the engine is a rocker arm, B,, Figs. 94 and 95, pivoted 
to the frame at its lower end A and carrying at its upper extremity the 




FIG. 99. — VERTICAL SECTION E-F. 



pin or shaft a. One end of this pin receives the rod from the fixed eccen- 
tric F, and the other end transmits the motion to the main valve, as shown 
in Fig. 95. The main valve has thus a fixed travel and governs the ad- 
mission and release just as in an ordinary slide valve throttling engine. 



THE BUCKEYE ENGINE 



95 



It is arranged to close the cylinder port at some predetermined point, say 
two thirds of the stroke, corresponding to the maximum horse power the 
engine is expected to develop. 

The cut-off valve consists of two narrow flat plates C C, Figs. 9G, 97, 
and 98, connected by rods and riding over seats formed on the back of 
the main valve. It is controlled from the governor eccentric through the 
medium of the two arms or rockers & h, pivoted on the main rocker arm 
R at point B, about midway of its length. (This is shown in detail in 
Fig. 100.) 

The skeleton diagram of Fig. 94 shows the engine on the crank-end 
center, with the governor eccentric in position for about one quarter 
cut-off. The motion of the cut-off valve is seen to be compounded of the 



TO MAIN VALVE 

FROM FIXED ECC. 




FROM GOV. ECC. 



FIG. 100. —SECTION SHOWING ROCKER ARM. 



motions of both fixed and governor eccentrics. Owing to the fact that 
its rocker is pivoted on the main rocker, it rides back and forth with the 
main valve; and it plainly has also a travel on the main valve, derived 
from its own or governor eccentric. The governor, as shown by Fig. 94, 
operates by varying the angular advance or by revolving eccentric G 
around the shaft instead of across it; so that the cut-off valve has a con- 
stant length of travel on the main valve, no matter what their relative 
positions or the point of cut-off. The main valve has also a constant 
travel, as it is driven by a fixed eccentric. This prevents the wearing 
of shoulders and is therefore conducive to tightness. 

The extreme positions of the governor eccentric are 45 degrees or more 
each side of the position of Fig. 94, and the cut-off may thus take place 
at any point from the beginning of the stroke up to the maximum cut-off 
allowed by the main valve, according to the position of the governor and 
the corresponding angular advance of eccentric. The arrangement is such 
that cut-off takes place near the middle of the cut-off valve travel, where 
the motion is fastest, thus giving a quick closure of the port. The stem 
of the main valve is made hollow to admit the cut-off stem, permitting 



96 



VALVE SETTING 



attachment to each valve to be made at its center of gravity. The area of 
the balance pistons is sufficient to hold the valve to its seat against the 
cylinder pressure, which is greatest during admission. 

This cylinder pressure becomes less and less during expansion, while 
the pressure due to the balance pistons remains constant, so that the valve 
is balanced during only a part of its stroke. To counteract the excess 
pressure of the balance pistons during expansion, recesses or relief cham- 
bers. Fig. 96, are cut in the valve seats and filled with live steam from 
the interior of the valve through holes y, thus allowing the steam pressure 
to get behind the valve and balance it. Channels z, cut clear across the 
valve face, prevent the steam from acting on too great an area and thus 
overbalancing the pistons; and at the instant of admission the valve un- 
covers recess x, as shown at the left hand of Fig. 96, leaving the valve 




EXHAUST CHAMBER- 
FIG. 101. — PISTON VALVE. 



to be balanced by the cylinder pressure during admission. Small coil 
springs behind the balance pistons hold the valve in place while steam is 
shut off the engine. It is not attempted to balance the valve entirely; 
enough excess pressure is allowed to hold the valve firmly to its seat. 

Owing to the positive valve gear, or the absence of releasing mechan- 
ism, it is possible to operate at any desired rotary speed. The engines are 
made in three types with long, medium, and short strokes, having rotary 
speeds of 60 to 170, 100 to 230, and 200 to 325 revolutions per minute, 
respectively. 

For tandem-compound and cross-compound engines the governor cut-off 
is usually applied to both cylinders, the valve stems of both main and cut-off 
valves being extended through from one valve chest to the other. 

For very high initial pressures and for the high-pressure cylinders of 
compound engines, the balanced piston valve of Fig. 101 is frequently used. 
It has the same general features as the balanced flat valve of Fig. 96. 
The main valve consists of two hollow cylinders connected by a series of 
bars, and having the outer ends closed. It takes steam into the interior 



THE BUCKEYE ENGINE 



97 



through the spaces between the rods and admits it into the cylinder 
through ports p, as shown. The exhaust passes out over the ends of the 
valve. The cut-off valve C consists of two 
short, hollow pistons or cylinders, rigidly 
connected, and working over ports p, on the 
inside of the main valve. Both main and 
cut-off valves are made tight by spring rings. 
The valve gear is identical with that pre- 
viously described. 

To secure quick admission and release 
with a small valve travel, multiported valves are sometimes used. This is 
usually done only on long-stroke engines of large size, simple valves with 
sufficient travel being preferred on small high-speed engines. Fig. 10^ 
shows a double-ported main valve. 




FIG. 102. 



Setting the Valves 



The operation of setting the valves is quite simple. First see that 
pin a at the upper end of rocker R vibrates an equal distance each side 
of its central position. This may be done by plumbing up from pivot 
A, Fig, 103, and measuring the distances a B and a G, which represent 
the horizontal travel of the pin. If these are not equal, adjust the fixed 
eccentric rod / until they are equal. For future reference, marks indi- 
cating the corresponding positions may be made on 
the hub or other convenient point, as shown, if they 
are not already there. 

Next place the engine on the head-end center, be- 
ing careful to take up all lost motion in the direction 
of rotation. 

Unhook the fixed eccentric / and place the rocker 
arm R in its central position. The main valve 
should then be in its central position on the valve 
seat. Now roll fixed eccentric around the shaft, to 
such a position hehind the crank that the next valve 
movement will be away from the crank, or contrary 
to the forward stroke of the piston, as shown in Fig. 
104; and couple the eccentric rod f to pin a of the 
rocker. Then leaving the engine on the dead center, 
roll eccentric F further around the shaft toward the 
crank until the outer edge of valve port p overlaps 
the inner edge of cylinder port P by the amount of 
the lead, or imtil the port edges are line and line, if there is no lead. The 
valve ports, crank, and eccentric will now occupy a position about as Fig. 




FIG. 103. 



98 



VALVE SETTING 



V 




v^ 




"♦-^ 



THE BUCKEYE ENGINE 99 

105. Lock the eccentric F in place and roll the engine around to the crank 
center; if the work has been accurately done, the valve will show proper 
lead on the crank end. Slight adjustments may be made by the valve stem. 
This completes the setting of the main valve. 

If the eccentric is but slightly out of place, it will be necessary only 
to adjust the eccentric to show proper lead. For the cut-off valve, first 
see that it makes the proper length of stroke on the main valve, adjust- 
ing eccentric rod g until it does. Then with the engine on the crank- 
end center, allow the governor to come to rest on its inner stops. This 
will revolve eccentric G backward on the shaft until its center about coin- 
cides with the crank. This is shown by Fig. 94, where the governor is in 
an intermediate position, the dotted lines representing the extreme inner 
and outer positions of the governor arms. The exact position of eccentric 
G when the governor is at rest will be fixed by the design of the engine; 
for condensing engines it may be a little ahead of the crank, while for 
heavily loaded engines not subject to great fluctuations of load, it may 
be a little behind the crank. 

Under ordinary conditions the crank and the governor eccentric should 
pass the dead center at the same time, in the same direction. 

Then with the engine on the crank-end center and the eccentric G 
coinciding with the crank, the cut-off valve should be in its extreme left- 
hand or head-end position, since the rockers h reverse the motion of the 
eccentric. If the valve does not occupy this position, adjust the valve 
stem until it does. With crank and eccentric still coincident, turn the 
engine over to the head-end center and see that the cut-off valve is in its 
extreme crank-end position. The point of cut-off is then determined by 
the angular advance of the eccentric, which in turn depends upon the 
adjustment of the governor. Eoughly speaking, for one quarter cut-off 
the governor should occupy such a position as to bring eccentric G about 
90 degrees ahead of the fixed eccentric. 



IX — ( Continued) 

THE BUCKEYE E^GmE— Continued 

The Buckeye Piston Valve 

The first part of this chapter treats of the older Buckeye engine with 
box type of valve. In this part of the chapter we wish to give the build- 
ers instructions for setting the valves on their newest type of piston valve 
with inside cut-off. 

Fig. 105A gives a sectional view of the cylinder and valves of this 
engine with the latter in position. It will be seen that the valve setting 




FIG. 105A. 



involves the same principles as explained for the box type of Buckeye valve, 
but as there are several points of difference in the details, the following 
instructions will be of value and necessity to the operating engineer: 



Setting Piston Valves 

The foregoing instructions for setting side valves are to a certain ex- 
tent inapplicable to piston valves, as none of the events can be observed 
by removing plates or covers, except where a guide stem works in a re- 
movable bonnet, as at the right of the cut, A. When this bonnet is 
removed the exhaust and exhaust closure CH can be observed. These 

■ 100 



THE BUCKEYE PISTON VALVE 



101 



conditions necessitated the system of marks which will be found on the 
valve stems with letters adjacent thereto, the meaning of which letters is 
as follows : 



On Cut-Off Valve Stems: 
CB, cut-ofP, l)ed end. 
C, center of travel. 
Oil, cut-off, head end. 



On Main Valve Stems: 
T T, ends of travel. 
LH, lead, head end. 
CB, compression, bed end. 
C, center of travel. 
CH, compression, head end. 
LB, lead, bed end. 

To Use ti-ie Marks 

Provide a parallel straight-edge of thin wood 
or metal, of siiitable length, and exactty 2 ins. 
wide. Eemove the packing from the stuffing 
boxes L, M, N, and shove the glands home 
against their collars and bind them there with 
followers. Then place the straight-edge against 
the projecting end of the gland and when its 
outer edge cuts any of the marks (except T T) 
the event indicated by it should be just taking 
place. 

Marks T T diO not indicate events, but ex- 
tremes of travel, and before testing by any of the 
others these must be cut b}^ the straight-edge at 
ends of travel. If such is found not to be the 
case, the adjustment required to correct will be 
found as follows : 

Setting the Main Valve and Eccenteic. 
-^First, test and correct the lengths of the valve 
connections — the eccentric rod and short connec- 
tion between the rocker arm and valve stem. If 
the eccentric has been set to marks, this is 
done b}^ equalizing the leads and compressions, 
particularly the compressions, but to make 
our instructions cover all possible cases we 
Avill suppose that the eccentric is out of po- 
sition by an indefinite and, unknown amount. 

In that case, the only test of the proper length of the rods is equal- 
ity of maximum admission openings, Avhich once equalized will remain 
so in all positions of eccentric. For this test the shaft is revolved 
to each extreme of the eccentric's travel in turn, the admission opening 




FIG. 105B. 



102 VALVE SETTING 

showing in each, ease (by marks on the valve, remember) measured and 
compared and if found unequal, the length of the connections changed 
by an amount equal to one half the difEerence between the two openings, 
lengthening or shortening as required so as to throw the valve toward 
the end at which the smallest opening was shown. For instance, suppose 
the smallest opening was shown at the " crank end," the connections should 
be shortened^ and vice versa. 

But instead of testing by equality of maximum admission openings as 
here stated, test by the marks. 

When the above adjustment is correctly made all subsequent ones must 
be made by turning the eccentric on the shaft, the length of the valve con- 
nections being then correct under all circumstances. 

To SET ECCENTRIC in correct angular position, place crank on one of 
its dead centers and turn the eccentric, if need be, till the mark LH or 
LB is cut by the straight-edge, according as the piston may be at the 
" head " or " bed " end of cylinder. This completes the set of the main 
valve, unless subsequent indicator tests should show the desirability of 
slight changes of adjustment. Thus if compression shows inequality, it 
is desirable to equalize them, though in doing so the equalization of marks 
T T has to be slight!}^ departed from. They are only as correct as they 
can be made v/ithout indicator tests. Equality of compressions is the end 
to be attained, though that is more a matter of looks on the diagram than 
of practical running qualities, as equalizing by the marks will equalize 
compressions accurately enough for all practical purposes. 

When the marks on the guide stem (as at the right end of the 
cut) are to be consulted, the bonnet and its gasket are removed and the 
straight-edge placed against the face of the chest when its inner edge must 
cut the mark to be consulted. 

Cut-off adjustments may be made as per Part I of this chapter, but if 
there is no steam pressure available for the method, the cutting of mark 
CH or CB by the outer edge of straight-edge will give the same indica- 
tion. Then proceed to time the cut-off in piston stroke, bearing in mind, 
however, that when a condenser is in use the governor wheel may have to 
be advanced to properly control the speed when running as lightly loaded 
as it is ever likely to be. 

The center of travel mark C on cut-off stem is of use only to bring 
about the conditions described. Part I, but in a different and simpler way, 
thus: when the mark is cut by the straight-edge as directed the wrist pins 
to which the main and cut-off valves are attached should be about in line 
with each other. 



X 
THE POETEE-ALLEN ENGINE 

This engine is of the four-valve type, and the special feature of the 
gear is the use of a link, actuated by a single eccentric and driving inde- 
pendently the steam and exhaust valves. 

There are two steam valves governing the admission and cut-off, and 
two exhaust valves governing release and compression. The two steam 
valves are placed vertically in a chest at one side of the cylinder, and 
the two exhaust valves are similarly placed in a second chest on the other 
side of the cylinder, as shown in the plan of Fig. 107. All the valves 
are driven by positive gear, and their movement is lengthwise of the 
cylinder. 

Figs. 108 and 109 are respectively horizontal and vertical sections of 
the cylinder and valve chests, and show the details of the valves. The 
valves are all balanced flat-side valves, working between the valve seat 
on one side and a pressure plate on the other. The movement of each 
valve covers or uncovers four openings for steam, two on the cylinder face 
and two on the outer face, as shown by the arrows in Fig. 108; so that 
only narrow seats and short valve strokes are required to give large edge 
opening. The opening movement of each valve is inward or toward the 
center of the cylinder. 

The arrangement of the valve gear is shown by the elevation and plan 
of Figs. 106 and 107, and the link detail of Fig. 110. The eccentric E 
is forged on the shaft and is coincident with the crank. The eccentric 
strap and the curved link L are made in one piece, as shown, and the 
link is pivoted at its central point on the trunnions t, which in turn are 
pivoted to the frame at the fixed point A. The vibration or horizontal 
movement of the trunnions is equal to the throw of the eccentric. In 
the slot of the link is the block B, from which are driven the two steam 
valves. The short rock shaft s on the frame is actuated by the outer arm 
a, which is connected by the steam rod with the block in the link. It 
carries on its inner end the two arms H and C which drive respectively 
the head-end and crank-end steam valves, through the medium of the 
two coupling rods li and c, and the two valve stems. The steam valves are 
offset in the chest, as shown by Fig. 106, in order that connection to each 

103 



104 



VALVE SETTING 



yalve may be made at its center of gravit}'; and short guides are provided 
at the connections of the levers H and C and tlie valve stems. 

An inspection of Fig. 110 will show that the link has a peculiar move- 
ment, composed of the horizontal and vertical throws of the eccentric. 




The link is restrained from rising by the trunnions, and the horizontal 
throw of the eccentric draws off the lap of the valve, while the vertical 
throw tips the top of the link alternately to and from the C3dinder, as 
the eccentric center rises or falls in its revolution, the upward throw tip- 



THE PORTER-ALLEN ENGINE 



105 



ping the link toward the cylinder and the downward throw tipping it 
from the cylinder or toward the shaft. This tipping of the link opens 
and closes the steam valves by rocking the rock shafts by means of the 
steam rod and arm a. 

This movement is shown by Figs. 106, 107, 111, and 112, the last 
two being in diagram and exaggerated for clearness. In Figs. 106, 107, 
and 111 the engine is on the head-end center; the head-end steam valve 
is open for lead, and the crank-end valve is closed, the eccentric, the link, 
and the arms a, H, and C being about in the positions shown. In Fig. 
113 the engine has made part of its stroke and the eccentric has reached 
the position shown. The upward movement of the eccentric has tipped 
the link toward the cylinder and the block is back of its former position, 




m-- 



FIG. 108. — HORIZONTAL SECTION OF CYLINDER. 

as shown by the dotted line dropped from Fig. 111. This has pushed 
arm a to the left, and has pulled the head-end valve to the right and 
wide open by means of arm //, rod li, and the lower connection. As the 
arm H is nearly in its upper or midposition, the slight angular move- 
ment of the rock shaft s results in a comparatively large horizontal move- 
ment and the valve is opened quickly. At the same time the arm C moved 
downward through the same arc as arms a and H, pulling the crank- 
end valve to the right; but, as arm C is about at the end of its travel, 
the angular movement results in only a very small horizontal movement, 
hardly moving the crank-end valve on its seat. Thus the valves are 
opened and closed quickly by the middle movement of their arms, and 
have very little movement while open or closed, as the arms are then at 
the extremes of the travel. As shown by Fig. 106, the position of the 
block in the link is under the control of the governor, a dropping of 
speed causing the governor balls to drop and so raise the block, and an 



106 



VALVE SETTING 



increase of speed forcing the block down toward the trunnions. When the 
block is at the top of the link, as in Fig. 110, the steam rod receives the 
full tipping motion of the link and cut-off takes place at the maximum 
point, about six tenths of the stroke. On the other hand, when the gover- 
nor balls are in the extreme upper position the block is forced clear down 
to the trunnions, and so receives none of the tipping motion of the link. 
Then the valve is merely opened for lead, and is closed immediately. 

Thus the steam valves are always opened and closed quickly at the 
midtravel of their arms; the velocity of cut-off increases as the cut-off 
is lengthened, since the block is higher in the link, and so corresponds 
to the increased piston velocity near midstroke; and the velocity of valve 
movement is increased directly with the speed of the engine. 

The well-known Porter fly-ball governor is used. It is carried on a 
bracket from the engine frame and is belted to the crank shaft. Its dis- 




FIG. 109. — SECTION AT A-B, LOOKING TOWARD CRANK. 



tinguishing features are light fly-balls with a high rotative speed, to secure 
sensitiveness, and a heavy ball or weight on the vertical shaft to secure 
the gravity effect required to keep the revolving balls in their effective 
plane. Its sole function is to raise or lower block B in the link. Since 
the valves are light, perfectly balanced, have a central draft or attach- 
ment, and small movement, very little force is required to move them and 
the load on the governor is small. 

The exhaust valves are placed in a separate chest on the crank side 
of the cylinder, opposite the steam valves. They have a fixed travel and 
are driven from a stationary point on the link by means of the exhaust 
rod, the rock shaft e, which passes through the engine frame, and the two 
arms E and F on the opposite ends of shaft e, as shown in Figs, 106 and 
107, They are so arranged that the opening movement of one valve and 
the closing movement of the other takes place at the middle of the vibra- 
tion of the arms where the motion is swiftest. 



THE PORTER-ALLEN ENGINE 



107 



One half of the exhaust valve movement is sufficient to give full port 
area for release, and this is accomplished hy the time the piston has com- 
pleted its forward stroke; so that the return stroke is begun with a wide 
open release port in front of the piston. Closing does not begin until 
the piston has accomplished more than half stroke, where its speed is 
diminishing, so that there is no throttling of the exhaust until just after 
port closure. 

The details of the cylinder valves and pressure plates are shown in 
Figs. 108 and 109, the latter being a section through the head-end valves. 




FIG. 110. — DETAIL OF LINK. 



and showing the steam valve on this end lower than on the other, as is 
also shown in dotted lines on Fig. 106. The valves consist simply of flat 
rectangular frames with a central bar for the attachment of the valve 
stem. 

The pressure plates of the steam valves are held between the side 
guides g g, Figs. 108 and 109 ; and in the other direction between a 
planed spot on the cover and the valve seat. Steep beveled seats are on 
the valve seats as shown, and the pressure plate is held in position by the 
adjusting screws or bolts 6, Fig. 109. 

The plates are adjusted by these bolts; screwing the bolts in forces 
the plate up and away from the valve; backing the bolts out lowers the 
plate and the steam pressure holds it against the valve. They are properly 
adjusted when, with steam on and all parts at the working temperature, 
the valves may be moved easily by the starting bar without leaking at the 
joints or seats. These plates are made hollow, as shown, to admit steam to 



108 VALVE SETTING 

the outer edges of the valves. The adjusting bolt has a hardened steel end 
which works on a hard-steel nut or socket in the pressure plate. The 
exhaust valves are also flat rectangular frames and are set lower than 
the bottom of the cylinder, in order to secure perfect drainage. 

The pressure plates for these exhaust valves are shown at the left in 
Fig. 109. They are not adjustable, as are those for the steam valves, but 
are bolted to the face of the valve seat. They are also made hollow to 
furnish ample exhaust passage. 

All four plates are made very stiff and rigid to prevent them from 
springing and leaking when subjected to the pressure. 

A removable cover over each valve affords ready access to valve, pres- 
sure plate, and seat. 

In short, the distinguishing features of this valve gear are flat-balanced 
valves at four points of the cylinder, the steam valves at one side and 
the exhaust valves at the other; all valves independently adjustable; a 
single eccentric with link motion and positive gear for all valves, with a 
fly-ball governor controlling the cut-off; an arrangement of gear whereby 
the valve motion is made to agree in velocity with that of the piston, 
and an ability to run at any speed, due to the use of positive gear. 

Setting the Valves 

The joint of the valve gear consists of hardened steel pins and hard- 
ened steel bushings in the rod ends; there is therefore no adjustment in 
the length of the rods and the valve strokes are determined and fixed 
when the engine is built, requiring no adjustment. 

To set the steam valves, first place the engine on the head-end center 
in the usual manner, taking up all lost motion in the direction of rota- 
tion. Block the governor up until the block B comes down to the center 
of the trunnions. Then remove the valve covers and set the head-end valve, 
by means of the valve stem, until it shows the proper lead — ■■^■^ in. or more 
— at that end, as given by the engine builder. Then turn the engine to 
the other center and set the crank-end valve to show the same lead. Now 
let the governor down, bringing the block to the top of the link. This 
will move the valve a short distance toward the crank, no matter which 
center the engine is on. This increases the lead at the head end and 
decreases it at the crank end, so that the lead at the two ends is varied 
according to the position of the block or the distance to which steam is 
carried. By varying the lead, the points of cut-off are equalized, and the 
correctness of the valve setting may be tested by blocking the governor 
in any position whatever, and turning the engine over throughout a com- 
plete revolution. The points of cut-off or the distance the piston has trav- 
eled when cut-off takes place will be the same for both forward and return 



THE PORTER-ALLEN ENGINE 



109 






110 VALVE SETTING 

strokes. This may be demonstrated by marking both crosshead and guide 
at cut-off on the forward stroke, and making a second cut-off mark on the 
guide the same distance from the dead center on the return stroke. When 
the crosshead reaches this second mark, on the return stroke, the valve 
should just close the port. 

It will be seen that the position of the trunnions, or, in other words, 
their vertical adjustment, is an important matter. To provide for accu- 
rate adjustment and to allow for wear of the shaft or other bearing, the 
pin on which these trunnions are pivoted is adjustable by the wedge Tc 
and bolt S, shown in Fig. 110. If the trunnions are not in line with the 
center line of the eccentric, the travel of both steam and exhaust valves 
will be affected and inequalities in all the functions will result. 

Further adjustments, shown by the indicator to be necessary, may be 
made by lengthening or shortening the valve stem at the socket near the 
guide shown in Fig. 106. The chest need not be opened. The exhaust valve 
motion is imparted by nonadjustable links and rocker arms; all that is 
necessary is to measure out on the guides, from each dead center, a dis- 
tance equal to the point of compression. Then place the engine on the 
forward stroke to such a position that the mark on the crosshead coincides 
with this point of compression; then, by means of the valve stem, set the 
crank-end exhaust valve line and line with its port. Turn the engine 
over until the crosshead mark agrees with the compression mark on the 
return stroke and set the head-end exhaust valve line and line. The dis- 
tance of the point of compression from the beginning of the stroke may 
be obtained from the engine builder, as may also the lead. When these 
are not known, adjustments in the proper direction must be made from 
a series of indicator diagrams, continuing the adjustments until the dia- 
grams show the proper outlines. 

Each valve is held between two pairs of nuts, the inner ones of which 
are flanged. When the valve is properly set, screw the inner nuts up to 
the valve just enough to take up lost motion without pinching the valve, 
and set up the outer or lock nuts tightly against the inner ones. 

Before replacing the chest covers after making adjustments, it is well 
to turn the engine slowly throughout an entire revolution, with the gov- 
ernor blocked up to the running position, and see that lead, cut-off, release, 
and compression take place correctly and that all parts move free and 
clear. A further trial with the governor clear up should show no steam 
opening except for lead. 



XI 

THE FITCHBURG EI^GINE 

The most distinctive feature of the Fitchburg steam engine is the valve 
motion, valve and governor design being next in importance. Although 
the designers and builders of these engines advocate moderate piston and 
fly-vi^heel speeds, the valve motion and governor are adaptable to all high 
speeds required of reciprocating engines. The number of this type of 
engine in use makes a study of its distinctive features worth the operating 
engineer's while. 

The general arrangement of the valve gear is shown in Fig. 113. The 
steam valves act separately, being operated by the governor eccentric by 
means of the rods A and B and the cranks C and D driving the cams by 
means of wrist cranks on the opposite ends of their shafts. The exhaust 
valves are on one stem actuated by a fixed eccentric on the engine shaft 
through the medium of the rods E and F. It will be noted that the exhaust 
eccentric and valve rods are so located that the movement of the eccentric 
is transmitted directly to the valve. 

Both steam and exhaust valves are adjustable to wear. The adjust- 
ment will be understood by reference to Fig. 114, which shows the details 
of one of the steam valves. A lengthwise section of the valve and the valve 
chest is shown in the lower figure, and the valve is shown removed at J, 
while a cross sectional view of the outer shell with tongue and inner cone 
is shown in the upper right-hand corner. 

The construction of the valve, as shown in the lower view, consists of 
the valve stem A, on which the valve parts are kept in place by the nuts 
B. The follower rings C and D fit into and bind in place the taper cone 
E E, which is used to set out the expansible ring F F. Adjustment bolts 
G G are used in connection with adjusting the valve to wear. 

To adjust the valve, first slacken the nuts B just enough to allow the 
ring F to expand slightly, then to expand it slacken the bolts G G 
and run the set screws H in until the required expansion is accomplished. 
If the first trial is not sufficient, continue until the proper adjustment is 
reached. If it is too tight, reverse the process by first slackening the set 
screws H and tightening the bolts G. While setting up or slackening the 
adjustment, keep trying the valve by rocking it back and forth with the 

111 



THE FITCHBURG ENGINE 



113 



starting bar. After the adjustment is completed tighten 'the nuts B and 
then see that the screws and bolts G and H are tight and evenly set up all 




= 


o 


V 


J 


J 


o 


' 




- 




- 


/ 


r" '- 


\ 




Sectional View of Packing Ringi 




Cylinder 



3 



FIG. 114. — LENGTHWISE SECTION OF STEAM VALVE. ALSO THE VALVE REMOVED, 
AND A SECTION SHOWING TONGUE. 



around. This method of adjustment applies to both steam and exhaust 
valves. • 

The Separate Steam and Exhaust Valves 

The separate steam and exhaust valves are shown in Fig. 115. The 
exhaust valve A is not usually ported while the steam valve B is double- 
ported and balanced, as shown in Fig. 114. In Fig. 115 the valve motion 



114 



VALVE SETTING 




'E 



W 




\i:Mq 



gnm-t p^t>^ 



is shoM^n in the center of its travel, with 
the valves lapped. While in this position 
the rocker arms C and D and cranks E and 
F should be vertical, or at exact right an- 
gles with the center line of the engine, with 
the cams G and H as shown and the valve 
rod so adjusted that the valves have their 
proper lap. When all the rods are properly- 
adjusted as to length the rocker arms and 
cranks will travel an equal distance on each 
side of the center line on which they rest 
in this cut. The nut J on the steam reach 
rod has a right-and-left thread in it and by 
loosening the lock nuts and turning the 
center, the length of this rod can be altered 
to bring the cranks in line. 

In Fig. 114 the steam valve is shown 
in the position where it is just opening (the 
arrows denoting the direction of the flow 
of steam). Fig. 116 shows the same valve 
opening; note the position of the cranks 
here. They are both at a middle position 
of travel in one direction. The governor 
eccentric is now at middle throw. One 
steam valve is opening and the other one is 
closed. When the positions are reversed 
and the eccentric is on the other center, the 
steam valve here shown open will be back 
in the position shown in Fig. 115, while 
the crank-end valve will be open. 

The exhaust valves are to be evened up 
on their rods and their eccentric so set 
that they close and open alternately at 
about seven eighths of the engine stroke. 

It will be noted that the extreme steam- 
valve travel is equal to the steam lap and 
nearly the width of main port (Fig. 115). 
The steam valve is given this travel through 
the medium of the cams, and herein lies the 
peculiarity of this valve motion. 

The largest part of the cam slot is of 
the same radius as the circle that the driv- 
ing pin and roll on the wrist crank pass 



THE FITCHBURG ENGINE 



115 



through, so that when the pin is moving down and away from the steam 
chest and back again to the position shown in Fig. 115, the valve is at rest. 
This is for a period of one half the engine revolution. To prevent a too 
sudden action of the valve, the slot is just enough off from the point M to 
the end to start the cam and valve in motion slightly before the valve opens. 

Steam Valve is Balanced 

As can be seen, the steam valve is balanced l)y having the steam pressure 
on all sides, with the exception of the amount of the area of the valve 
stem on the one end. 

This exception acts as an assistant in obtaining quick cut-off for the 
pressure on the outside end of the valve is just enough more than that on 



_, m 




^^^mm ^M^mmm. 



1 



FIG. 116. 



the other end to force the valve back without the aid of the cam motion, 
when the return begins. This is evidenced by the fact that when steam 
pressure is on the cam is kept pressed against the driving roll at all times 
and after long use there is no sign of wear on the back side of the slot. 

The steam valve admits, and the exhaust valve releases, steam over 
the inside ends. The steam-valve motion is indirect, on account of the 
cranks, and the exhaust motion is direct. With one eccentric the exhaust 
valves would necessarily have to release over the outside ends, but as the 
eccentrics are separate the exhaust release is as stated. For this reason the 
governor and exhaust eccentrics both lead the cranks. 

Fig. 117 shows the relative position of the crank pin and steam eccentric 



116 



VALVE SETTING 



at about the point A on the dotted line R A, or it is about 90 degrees plus 
37 degrees for lap and lead ahead of the crank, and the exhaust eccentric 
is approximately at 90 degrees ahead of the crank. This latter fact may- 
be useful to know in the event of a slipped eccentric and the minimum 
time for adjustment. 

Fig. 115 shows both eccentrics at 90 degrees, while Fig. 116 shows the 
lead of the steam valve distorted, for clearness of illustration, but the 
valve crank is in the same position as when the crank pin is a little by the 

center and the eccentric is ad- 
vanced a little beyond the point 
shown in Fig. 117. When in this 
position the steam is cut off at 
about one-fifth stroke or in full 
travel about three-fourths stroke. 
The angle of advance increases as 
the eccentric is thrown across the 
shaft by the action of the governor 
as speed tends to increase, thus 
accomplishing the regulation of 
speed. For a full understanding 
of this action refer to Fig. 117. 
The action is as follows : As long 
as the engine is below speed, the 
eccentric is kept in its longest 
throw by the tension of the 
springs and steam follows about three fourths of the stroke, but as 
soon as the proper speed is reached centrifugal action causes the weights 
H to overcome the tension of the springs and to move outward, at 
the same time lengthening the springs; by means of the connecting 
rods G G the outward motion of the weights turns the suspension arms 
C upon their fulcra and through the ears B the eccentric is carried 
across the shaft from 8 toward R, and as the arcs described by the centers 
B B are in opposite curves they compensate each other, and the center 
S of the eccentric follows a straight line in its movement, preserving a 
constant lead opening or otherwise as desired. This manifestly decreases 
the eccentricity, and increases the advance of the eccentric, giving an earlier 
cut-off to the valve until, when the eccentric is swung squarely back of the 
crank, the valve opens only the lead, there being all points between this and 
extreme cut-off for variation. Upon the least diminution of speed the 
springs have more power than the centrifugal force of the weights, and the 
motion of the parts is arrested and turned in the opposite direction, giving 
a later cut-off, as more work is performed by the engine. 





^ , 




J^GCf, 


^^ 


^ 




fe^ 


^■' 


IS ^ — f j 

\m, (Mi j& 


^P^-^''i 


r 



FIG. 117. 



THE FITCHBURG ENGLNE 117 

How TO Set ak^d Adjust the Valves 

Having now discussed the motion, the idea is to get a working knowl- 
edge of liow to set the valves and adjust them and the governor for various 
conditions. 

The builders give the erecting men a set of instructions for their guid- 
ance when first setting up the engine, extracts of which, given herewith, 
should with the foregoing afford a working knowledge of the adjustment 
of these engines, under any conditions, to the operator. 

The location of the governor case is determined by placing the engine 
on one dead center and rolling the case around the shaft until the offset 
of the eccentric is on the opposite side of the shaft from the crank pin. 
Then roll carefully into such position that when (with the springs re- 




FIG. 118. 

moved) the eccentric is thrown back and forth across the shaft, no end 
motion is given the valve rod. At this place tighten the governor case 
firmly upon the shaft and roll the shaft to the opposite dead center and 
again move the eccentric back and forth across the shaft, and if there is at 
this end any end motion to the valve rod change the position of the gov- 
ernor case on the shaft enough to make the motion just half as much, then 
fasten the governor case firmly in this final position by drilling into the 
shaft for the point of the set screw and then tightening the clamp bolts 
to place solidly. Put in the springs and tighten them until the proper 
number of revolutions is obtained, being sure to tighten up the springs that 
go through the counterbalance which hangs nearest the springs (when the 
governor is at rest) about three fourths of an inch more than the springs 
on the other side. 

The travel of the exhaust valves can first be evened up, before their 
eccentric is tightened upon the shaft, by rolling the eccentric around the 
shaft to its extreme throw at each end. It should then be set so that the 



118 



VALVE SETTING 



port is just closed when the crosshead has traveled a little less than seven 
eighths of its stroke, and the set screw firmly screwed upon the shaft. 

To adjust the steam valves, place the latch of the hook in the center 
of the half spiral slot and clamp the hook firmly by its lever, evening up 




FIG. 119. 

the movement of the wrist cranks by the right and left nuts in the valve 
rod, so that in a revolution of the engine shaft they rock evenly each side 
of a vertical line drawn from centers of their shafts; set the engine ex- 
actly on the head center and move the small valve rod attached to the 
head valve in or out of its cam until the port is opened the proper lead 
(in usual cases -jV of an inch), and tighten the set screw in the neck 
of the cam upon the rod firmly. Eoll the engine to opposite center and 




FIG. 120. 



set the other valve in the same way. After the valves are thus set as 
closely as possible they should, if practicable, be adjusted by use of the 
indicator when the engine is under partial or full load, as no mere meas- 
urements can ever set the valves exactly right in any engine. The exhaust 
valves of the low-pressure cylinder can be set the same as for the high- 
pressure cylinder. 



THE FITCHBURG ENGINE 119 

The shaft governor depends for its action upon the centrifugal power 
of the two weights nearest the rim, which, through the connecting rods, 
move the counterbalancing weights to which the eccentric is attached and 
thus carry the eccentric across the shaft, altering the throw of the valve 
rod and the point of closure of the admission valves. The centrifugal 
power of the weight arms is exerted against the springs, and as the point 
of cut-off is earlier the more the weight arms are thrown out toward the 
rim it follows that to increase the speed of the engine, the springs must be 
tightened or the weight reduced; and to decrease the speed, the springs 
must be loosened or the weight increased. The springs should not be 
stretched much over 1-J times the length of the coil when unstretched. The 
engine can be changed several revolutions by adjusting the tension of the 




FIG. 121. 

springs, but if a marked change is desired, confer with the builders and 
they will direct what should be done. Care should be taken that a little 
even friction be maintained between the face of the eccentric and the gov- 
ernor case to prevent dancing, and this is secured by the springs and wash- 
ers on the ends of the pins which carry the counterbalance weights. Once 
adjusted they are right for a long time. 

Adding to the centrifugal weight arms and increasing the tension of 
the springs make the governor more sensitive. Do not make radical 
changes in the weights or springs of the governor without consulting with 
the builders. 

Practical Illustration of Setting Valves 

i\-n illustration of valve setting on this type of engine is given in 
the following experience. On indicating the engine a friction-load dia- 
gram such as is shown in Fig. 118 was taken. The head-end diagram 
showed some 30 lbs. less initial pressure than on the crank end, the lead 
was late and the cut-off early. To even up the initial pressure on the 
two ends, the reach rod to the wrist cranks was shortened by turning 



120 



VALVE SETTING 




J^IG. 122. 



the nut J, Fig. 115. This had the effect of more lap on the head-end 
steam valve and less on the crank end, giving the diagram in Fig. 119, 
where the initial pressures were broiight within 8 lbs. of each other 

by the change. It will be noted that the 
head end had the latest cut-off by the change. 
Before making further changes, the diagram 
Fig. 120 was taken with about one-third load 
on the engine. Under these conditions the 
initial pressure is about equal, with the cut-off 
still late on the head end. 

The valve stems enter the cams a straight 
fit and are secured by a set screw. The crank-end valve stem was loosened 
up in the cam and set out a trifle to give the effect of less lap. The dia- 
gram Fig. 131 was then taken under the same conditions as Fig. 130 and 
shows the cut-offs to be about even. 

In conclusion it may be well to mention that in keying up any of 
the pin bearings of this engine a wedge adjustment 
is used. On both ends of the connecting rod is a 
box, shown in detail in Fig. 133. To set up on 
these boxes, loosen the bolt B and tighten A. A good 
way to work this adjustment is to slacken 5 to a 
considerable extent, then with the flat side of the 
wrench tap it down lightly until it seems tight, then 
take up the slack, on the bolt A just enough to know 
you have it set up, then screw B down into place, set- 
ting it up tight. 

The arrow marked on the outside end of every 
box connection denotes the direction the wedge should 
be moved to take up lost motion. To slacken, reverse 
the above operation. Fig. 123 shows the crosshead of 
these engines where the adjustment of the shoes is the 
same. On the end of the gibs arrows are stamped, 
which also denote the direction to key up the wedge. fig. 123. 




XII 



THE FLEMING PISTON-VALVE ENGINES* 



To set the valves of a Fleming piston-valve engine, it is necessary in 
the first place to get reference marks on the fly wheel corresponding to the 
dead-center positions of the piston. The method of obtaining these has 
been so frequently described that it seems almost unnecessary to repeat it 
here. We will, hoM^ever, give the method, since it constitutes a part of the 
operation of the valve setting. 

Turn the engine. in the direction it runs until the piston is within, say, 
an inch of the end of the stroke ; tram the fly wheel from some fixed point. 




FIG. 124. 

such as the subbase extension, and make a center-punch mark at each end 
of the tram, as at A and B, Fig. 124. Now make a mark on the edge of 
the lower crosshead shoe and one exactly in line with it on the lower 
guide ; then turn the engine in the direction it runs until these two marks 
coincide again. Tram the wheel again from the same point, B, on the 
extension, making a center-punch mark on the rim. Now find a point 
midway between the marks on the wheel with a pair of dividers. Turn 

* Contributed to Power, by Thomas Hall. 
121 



122 



VALVE SETTING 



the engine over until the tram just reaches this central point on the fly- 
wheel rim, and yon will have the dead-center position of the crank for 
that end of the stroke. Use the same method to find the other dead center. 
After the centers have been located, remove the valve from the steam 
chest or valve chamber, and make an accurate templet of the " head end " 

and " crank end." Such a templet 



Exhaust VJUge 



Steam ^ge. 



FIG. 125. 




Face of 
Valve Chamber 



is shown by Fig. 125. Also make a 
correct templet of the valve seat, in 
the valve chamber, making one end 
of the templet even with the face of 
the valve chamber. Fig. 136. Mark 
the ports, head end and crank end, 
showing both edges of both ports 
and the face of the valve chamber, as 
shown by Fig. 127, where E repre- 
sents the exhaust edges, and 8 the 
steam edges. 

These templets can be made 
from any light material, such as 
sheet zinc, sheet tin, thin strong 
pasteboard, or thin wood strips, but 
the edges, if made of wood, to insure accuracy, should be made of knife- 
edge form. 

After the templets have been made, the valve can be placed back in the 
valve chamber and connected up, locating approximately. Now turn the 
engine on one of the dead centers and proceed to adjust accurately. 

Fig. 128 shows the governor wheel on the crank-end and center position 
for a right-hand engine running over, the broken horizontal line through 
the center being the center line of the engine. The governor is shown in 
its position of minimum travel by the dotted lines, and of maximum travel 
by the full lines. Block the governor in its minimum position, turn the 
engine onto the crank-end center, take measurement from the end of the 
valve to the face of the cylinder, as shown by Fig. 129, and transfer this 
measurement to the templets, as shown by Fig. 130, when the amount of 



FIG. 126. 




Crank End Port 



Head End^Port Face of 

Valve Chamber 



FIG. 127. 



lead for the crank end can be readily seen and measured from the templets. 
The amount of lead will vary with the size of the engine and the steam 
pressure nsed, from gV to ^ of an inch on the head end, and practically 
double this amount on the crank end for noncondensing engines. 



THE FLEMING PISTON-VALVE ENGINES 



123 



On condensing engines with the governor in this position and the crank 
on the head-end center, the valve vrill have from gV to tV of an inch lap, 
or negative lead, according to the size of the engine and the steam pres- 
sure used, and should be about line and line on the crank-head center. 
The lead increases considerably as the point of cut-off increases. 

Upon turning the engine over in the direction in which it runs, with 
the governor in its minimum travel position, until the greatest movement 




FIG. 128. 



of the valve is obtained, the opening must not be sufficient to cause the 
engine to run away when the load is thrown off; i.e., it should be more 
than sufficient to overcome the friction of the engine. In order to insure 
this, the lead or port opening for this position of the governor should be 
but little, if any, greater than that specified above. 

The blocking of the governor should now be changed, fixing it in such 
a position as will give about } cut-off, approximately the point of cut-off 
corresponding to the rated load. This point of cut-off should be located 



124 VALVE SETTING 

on the guides by making marks on the lower guide line with the mark on 
the crosshead shoe for each dead-center position, and dividing the distance 
between them into three equal parts. Now turn the engine over until the 
mark on the crosshead shoe is in line with the new point of the guide, 
corresponding to ^ cut-off for the head end. You should now block the 
governor so that the valve is line and line at the steam edge by taking the 
measurements from the templets as above described. 

Next turning the engine over until the valve shows the cut-off on the 
crank end, when it will be noted that the crosshead has not traveled the 
full ^ stroke, as indicated by the crosshead and guide marks, by from ^ to 
^ of an inch, depending upon the size of the engine. An adjustment of 
the valve endwise will, of course, lessen this amount, but will increase the 
differences in lead between the two ends, so that this adjustment must be 
made to the best advantage, lead and cut-off considered. 

To determine the greatest port opening for any point of cut-off, the 
governor can be blocked for the desired cut-off and the engine turned over 
until the valve begins to change direction, and you will have the position 
of maximum port opening for that particular cut-off. 

In valve setting always turn the engine over in the direction it runs, 
never turning it past a point you desire to measure and then turn back to 
it, as the lost motion will affect accurate adjustment. 

To get the point of cut-off, or to get the position of admission, place 
the templet of the valve on the templet of the ports to a position where 
the steam edge of the valve is in line with the steam edge of the port. Take 
a measurement from the end of the templet corresponding with the face 
of the cylinder to the end of valve, and transfer this measurement to the 
valve in the valve chamber, as shown in Fig. 129. Block the governor in 
such a position that this measurement corresponds to that just taken from 
the templet. The maximum cut-off is usually about f stroke. 

It is advisable, but not absolutely necessary, to determine by measure- 
ment all events of the stroke including lead, port opening, cut-off, release, 
and compression, and make a note of each measurement for both ends of 
the stroke, so as to make ready comparison. Eelease will be earlier on 
the crank end than on the head end, and compression will be earlier on 
the head than on the crank end. Both of these events by measurement will 
probably be uneven by from -J to 1 in., depending on the size of the engine 
and the point of cut-off considered. The nearer to the end of the stroke 
these events occur, the less will be this difference. 

If great care is taken in setting the valves by the use of templets, when 
an indicator is placed on the engine and cards taken, there will be little 
adjusting to be done. There is no reason why an engine cannot be set in 
good running condition by the above method without the assistance of an 
indicator if the work is carefully done. 



THE FLEMING PISTON-VALVE ENGINES 



125 



CoMrouND Engines 

In taking np valve setting on compound engines, the first point to 
consider is what work the engine is designed for, what steam pressure it is 
to work under, and whether it is to run condensing or noncondensing. 

With regard to tandem compounds, wo will consider the two types of 
a valve gear; first the one in which the valves in both high- and low- 
pressure cylinders are controlled by the governor. In this type of engine 
the setting of the valves is practically the same as for the simple engine. 




klm|nii2[ 



FIG. 129. 



Of course both valves in the high- and low-pressure cylinders would be 
set independently, giving each its proper amount of lead; but since the 
governor controls both high- and low-pressure valves, we have an increased 
lead, as the cut-off becomes later for both valves. The load for the high- 
pressure valve should be practically the same as for the simple engine, 
while that of the low-pressure cylinder is usually from three to four times 
this amount in order to get the cut-off late enough and give ample port 
opening. 

A condensing engine has usually a higher cylinder ratio and cuts off 
earlier in the low-pressure cylinder than a noncondensing engine, so that 
the low-pressure valve of a condensing engine should have less lead than 



126 



VALVE SETTING 



a noncondensing engine. Compression rises less rapidly in the low-pres- 
sure cylinder of a condensing engine than in a noncondensing engine, so 
that compression should start earlier in the stroke of a condensing engine; 
this, of course, throws the release later in the low-pressure cylinder of a 
condensing engine than a noncondensing engine. 

It would be difficult to state here how much lead to give the low- 
pressure valve, as we would have to take some specific engine working 
under some fixed conditions. In this type of engine the load will remain 
practically uniformly divided between the cylinders throughout the full 
range of cut-off from minimum to maximum. 

The above construction, where the governor operates both valves, is 
seldom used except on small engines. It is not quite as flexible for adjust- 
ment as where the low-pressure valve is operated by an independent 
eccentric. 

With an engine of this type, where the valve on the high pressure is 
operated by the governor, and the valve on the low pressure by a separate 




Port 
Face of Valve Chamber 



FIG. 130. 



eccentric, as shown by Fig. 131, proceed to set the high-pressure valve 
in the same manner as that of a simple engine. Fig. 131 shows the 
eccentric used on the low-pressure valve in its position of maximum travel 
with relation to the crank for a right-hand engine running over. This 
eccentric is so constructed that its center, when adjusted, travels across 
the shaft, thus changing the cut-off in the same manner as in the high 
pressure. 

In Fig. 131, CD is a line running through the center of the crank 
shaft. A 5 is a line running through the eccentric center and its point 
of suspension. If the eccentric is so arranged that the center line of the 
eccentric, A B, is brought over or made to coincide with the center line 
C D, you will have the eccentric at its minimum point of cut-off. 

To set the low-pressure valve, first locate the eccentric at its point of 
minimum cut-off, or, in other words, have the points G H F and the 
crank (low-pressure crank if it be a cross compound) in a straight line. 
Fasten the eccentric with the set screws I and J, then turn the engine over 
in the direction in which it runs and test for the lead, point of cut-off, etc. 
For the best adjustment, have the point of suspension F slightly behind 
the crank, so that when the eccentric is moved by the screw in the slot from 
one extreme to the other, the lead remains nearly constant. Then adjust the 



THE FLEMING PISTON-VALVE ENGINES 



127 



screw E for the point of cut-off desired by giving the eccentric a greater 
throw and consequently the valve more travel. 

The above applies to the cross-compound engines as well as tandem 
engines, with the exception that, when setting the eccentric on the low- 
pressure cylinder in a cross-compound, the eccentric must be set with refer- 
ence to the crank on the low-pressure side. 

An early cut-off in the low-pressure cylinder will cause a high-receiver 
pressure and a late cut-off a correspondingly low-receiver pressure. It is 



C— 




Crank Pin ^^^B 



Cyl. End 



FIG. 131. 



advisable to so adjust the cut-off in the low-pressure cylinder, and conse- 
quently the receiver pressure, that the load will be evenly divided between 
the high- and low-pressure cylinders for rated load conditions. For very 
light loads the high-pressure cylinder will then carry somewhat more than 
half the load, and for overloads, the low-pressure cylinder will do slightly 
more work than the high-pressure cylinder. 

This is not at all objectionable, either from the viewpoint of economy 
or otherwise, as repeated tests of these engines have shown. The varia- 
tion in the division of the load is comparatively slight. 

The accompanying table, showing the effect of changing steam or in- 
side lap, exhaust or outside lap, travel and angular advance, for piston- 
valve engines is appended for convenient reference: 



128 



VALVE SETTING 





Admission 


Expansion 


Exhaust 


Compression 


Increase 
Inside Lap 


Is later 
Ceases sooner 


Occurs earlier 
Continues longer 


Is unchanged 


Engines at 
same point 


Increase 
Outside Lap 


Unchanged 


Begins as before 
Continues longer 


Occurs later 
Ceases earlie 


Begins sooner 
Continues longer 


Increase 
Travel 


Begins sooner 
Continues longer 


Begins later 
Ceases sooner 


Begins later 
Ceases later 


Begins later 
Ends sooner 


Increase 
Angular 
Advance 


Begins earlier 
Period unaltered 


Begins sooner 
Period the same 


Begins earlier 
Period unchanged 


Begins earlier 
Period the same 




FIG. 132. — VALVE GEAR OF THE PUTNAM ENGINE. 



XIII 



THE PUTNAM ENGINE.* 



The high-pressure, variable cut-off engine built by the Putnam Ma- 
chine Company, of Fitchburg, Mass., and known as the Putnam engine, 
presents distinctive valve-gear features which should interest the operating 
engineer. There are four " double-beat " poppet valves, all operated from 
a single lay shaft running at one half the speed of the main shaft, with 
a range of cut-off from to full stroke. A general idea of the valve gear 

may be obtained by examination of 
Fig. 132, which shows the back or 
valve-gear side of a left-hand en- 
gine cylinder. A sectional view of 
the valves and steam passages is 
shown in Fig. 135. A diagram of 
the side shaft is shown in Fig. 134, 
valves 2 and 3 being the steam 
valves and 1 and 4 the exhaust 
valves. 

To set the valves of a Putnam 
engine, first attach the regulator to 
the valve gear, raising the balls of 
the regulator as high as they will 
go and holding them in that posi- 
tion (see Fig. 133). Then push in 
the steam levers of valves 2 and 3 
far enough to allow the cams which 
operate them to be turned around 
on the shaft, just clearing the levers 
without lifting the valve as sho'wn 
in Fig. 133. While the levers of 2 
and 3 are in position, tighten the set screws in the rocker arm E, Fig. 133, 
at the bottom of the regulator, when the balls may be lowered (Fig. 137) 
and the regulator adjustment is complete. 

These directions regarding the regulator refer to the old-style regu- 

* Contributed to Power, by F. L. Johnson. 
130 




FIG. 133. 



THE PUTNAM ENGINE 



131 




T 'ON 



132 



VALVE SETTING 



lator; the new-style regulator, Fig. 136, is somewhat different and is 
operated in the following manner: After all the connections have been 
made, raise the balls until the clearance S, between the center weight and 
the collar, is ^ of an inch. Hold in that position and push the levers of 
2 and 3 in far enough to allow the cams to operate as with the old-style 
regulator. 

If the engine is to " run over," the bevel gear at the end of the lay 
shaft should occupy the position of E, Fig. 133. If the engine is to " run 




FIG. 135. — SECTIONAL VIEW OF VALVES AND STEAM PASSAGES. 



under," the positions of the collar D, Fig. 131, and the gear are exchanged. 
The lay shaft revolves in the same direction in all cases. The changing 
of the position of the gear changes the direction of rotation of the engine 
shaft. The question of direction of rotation being settled, the gears are 
made secure in their respective shafts, and the crank pin put on the center 
nearest the cylinder. 

Beginning at valve 2, Fig. 134, with the valve closed, make a mark on 
the valve stem ^V o^ ^^ i^ich below the packing box, turn the cam by hand 
in the direction it is run (Fig. 138) until the mark on the valve stem is 
flush with the stuffing box and make the cam fast to the shaft by means 
of the set screw. This will give yV'i^' valve opening when the crank is 



THE PUTNAM ENGINE 



133 



on the center. With the cam of exhaust valve 4 proceed in exactly the 
same manner as with steam valve 2, except that the mark on the stem 
should be -^-^ of an inch below the packing box. Be sure that the set 
screws in both 2 and 4 are set up securely and the crank is opposite center. 




FIG. 136. — NEW-STYLE REGULATOR. 



FIG. 138. 



Proceed with steam valve 3 exactly as with 2, allowing only 3V of an 
inch lift to the valve. The reason for doing this is because the piston 
travels much more slowly in the crank end of the cylinder than in the 



134 VALVE SETTING 

head end and does not need the same amount of lead to secure full steam 
pressure at the beginning of the stroke. Exhaust valve 1 is set the same 
as 4, with ir-iii- rise. 

The rock shaft which operates the cam levers of 2 and 3 is provided 
with leather-lined caps to the bearings, which are intended to furnish the 
necessary friction to prevent unsteady action of the regulator. These caps 
should be tightened just enough to produce the desired steadiness and no 
more, for if undue friction is induced the governor will be prevented from 
responding quickly to a change of load, and the motion of the engine will 
be unsteady. 

The foregoing instructions are intended to serve for setting the valves 
as accurately as can be done without the use of the indicator. After the 
engine is in operation the indicator should be used to check the work and 
secure accuracy. 



XIV 
THE STUKTEVANT COMPOUND EJ^GINE * 

The setting of the valves and the adjustment of the governor and 
drainage systems of any make of engine may well be preceded by a very 
brief description of its leading characteristics. As shown by the accom- 
panying sectional view. Fig, 139, the engine in question is of the vertical 
cross-compound type, with the cranks at 180 degrees. 

The high-pressure cylinder has a balanced piston valve working in a 
removable bushing which contains the ports; it takes steam on the inside 
and exhausts at the ends; auxiliary ports in the valve (see Fig. 147) 
increase the port opening, during the admission period, preventing wire- 
drawing. The piston valve is controlled by an inertia governor which is 
a modification of the Eites type, therefore the cut-off in the high-pressure 
cylinder is automatically changed according to the load. 

The low-pressure slide valve is balanced by means of a back platen 
maintained in position by six springs, three of which are shown at A, B, 
and C, Fig. 1-10. These springs fit the holes D, E, and F in the valve- 
chest cover. The low-pressure valve is not connected to the governor, and 
as the angular advance is constant, the cut-off in this cylinder does not 
vary with the load, but is fixed. However, the low-pressure eccentric is 
adjustable; that is, the throw may be changed by the engineer while the 
engine is not running. The adjustable eccentric permits changing the lead 
and cut-off, for altering the valve travel alters these events. The low- 
pressure cut-off occurs at practically one-half stroke for normal load. 

It is well to set the low-pressure valve first, for this operation is much 
easier than in the case of the high-pressure side. It is first necessary to 
remove the tap bolts and take off the covers leading to the low-pressure 
valve chest, the crank case, the valve-rod guide, and the eccentric ; these are 
showTL at A, B, and C, Fig. 141, and at D, Fig. 144. The low-pressure 
crank pin should be put on the top center, following any of the approved 
methods. A simple operation which quickly gives the position with suffi- 
cient accuracy for preliminary valve setting is to turn the governor wheel 
by means of the bar until the face A, Fig. 142, of the connecting rod is 
parallel to the front surfaces B, B of the crank arms. 

* Contributed to Power, by Carl S. Dow. 
135 




FIG. 139. —SECTION THROUGH CYLINDERS AND VALVES. 



THE STURTEVANT COMPOUND ENGINE 



137 




FIG. 140. — BACK PLATEN OF LOW- 
PRESSURE VALVE. 



The throw of the low-pressure eccentric should now be adjusted, the 
angular advance having been fixed when the keyway was cut in the eccentric 
hanger which is shown in Fig. 143. 
But before this can be done the 
direction of rotation must be de- 
termined. As the observer is now 
facing the low-pressure end, the 
engine is running under if turning 
clockwise. If the engine is to run 
in this direction (under), move the 
eccentric, which is fulcrumed to its 
hanger at F, and fasten the pin P 
at the extreme left-hand end of the 
slot *S^. This gives the eccentric 
maximum throw and the valve full 
travel. Of course the pin P should 

be fastened at the other end of the slot if the engine is to run over. When 
the pin P is in the center of the slot, as shown in Fig. 143, the valve has 
minimum travel and no lead, because the lead decreases as the pin ap- 
proaches the center of the slot, for this operation decreases the valve travel. 
With the eccentric fixed for full throw and the low-pressure crank pin 

on the top center, adjust the slide 
valve for a lead of -/g- in. at the 
top, that is, the narrow opening 
between the top edge Y of the valve 
and the lower edge X of the port 
should be -^^ in. See Fig. 141. 
This adjustment is made by alter- 
ing the length of the valve rod by 
means of the nuts at N. Both 
these nuts are shown at the right- 
hand side of the large section of 
the engine. Fig. 139. The low- 
pressure crank pin should now be 
put on bottom center. The lead at 
the bottom should be ^ in., or, as 
shown in Fig. 144, the distance 
{M N) between the edge of the 
port and that of the valve should 
be ^ in. If not, equalize the error 
by changing the leads, making one 
FIG. 141. -LOW-PRESSURE VALVE SIDE ^^^If the difference at the top and 
SHOWING LEAD ON TOP END. One half at the bottom; always re- 




138 



VALVE SETTING 



membering that the bottom should have a little more lead than the top. 

The low-jaressure side is now adjusted. 

Before setting the high-pressure valve the governor must be considered. 

The general appearance of this form of inertia governor is shown in Figs. 

145 and 146^ the former being a 
view of the side next the engine. 
The eccentric is not keyed to the 
shaft, but is free to move across 
it because of the slot, thus chang- 
ing the angular advance and con- 
sequently the cut-off. The eccen- 
tric and weight arm of the governor 
are both rigidly fastened to a stud 
S, which passes through the hub of 
the governor wheel ; the eccentric is 
thus compelled to move with the 
weight arm and its position varies 
as the stud moves nearer or farther 
away from the shaft center, due to 
inertia and centrifugal force. The 
disk D, Fig. 145, is the oil guard 
and has nothing to do with the 
action of the eccentric. When the 

governor wheel is stationary the tension of the spring is such as to allow 

the weight M to rest against the stop T, Fig. 146, in which position the 

valve has maximum travel and maximum lead. 




FIG. 142. — AN EASY METHOD OF PUT- 
TING THE ENGINE ON CENTER. 



To Set the High-pressuee Valve 

To set the high-pressure valve the valve plug V, Fig. 146, and the cover 
at D must be removed. With the piston valve enveloped by its bushing, 
it is impossible to see the valve itself, except at the top, and consequently 
the lead cannot be measured directly as in the case of the plain slide valve. 
The setting is accomplished by measuring the distance from the top of 
the valve to a given surface, which in this engine is the top of the valve 
chest with the plug or cover removed. The reference edge is shown at T, 
Fig. 147. 

Since the piston valve takes steam on the inside, the inside edges of 
the ports in the bushing are the important ones. Evidently the lead is the 
distance the inner edge of the valve has moved froni the inside edge of the 
port when the crank is on the center ; therefore when the valve is properly 
set the measurements must show that the desired lead exists in the valve 
chamber. 





FIG. 143. — ADJUSTABLE LOW- 
PRESSURE ECCENTRIC. 



FIG. 145. — THE INERTIA 
GOVERNOR. 




FIG. 144. — LOW-PRESSURE VALVE SIDE 
SHOWING LEAD ON BOTTOM END. 



FIG. 146. — THE GOVERNOR IN 
POSITION. 



140 



VALVE SETTING 



The high-pressure crank should be placed on the top center. The lower 
edge of the upper port is 5f|- ins, below the top surface T of the valve 
chamber. Since the thickness of the valve, measured from its top surface 
to the steam edge, is 2j\ ins., the top of the valve should be 3^ ins. from 
the reference edge T, to give a lead of \ in. This may be shown as follows : 




FIG. 147. — THE HIGH-PRESSURE VALVE. 



5^ — 3y\- — ^ = 3^. It is well to remember in this connection that the 
valve rises to open, hence the lead (^ in.) is subtracted from the distance 
of the top of the valve to the edge T (see Fig. 147). 

To set the valve, then, it is only necessary to put the high-pressure crank 
on the top center and adjust the length of the valve stem to make the top 
of the valve 3:^ ins. from the top of the valve chamber. As in the case of 



THE STURTEVANT COMPOUND ENGINE 



141 



the low-pressure valve, the stem is lengthened or shortened by means of the 
nuts on the stem at the slide. 

It is not necessary to determine the lead at the bottom, because the valve 




FIG. 148. — THE INDICATOR RIG. 



and its bushing are designed to give proper lead at the bottom when the 
top lead is ^ in. The same method of measuring is followed, the only 
difference being due to the location of the lower port. 



142 VALVE SETTING 

After replacing the covers and connecting the cylinder drains to the 
sewer, if the engine is to rnn noncondensing, or to the exhaust pipe if con- 
densing, the start may be made. The reason for connecting cylinder drains 
to the exhaust pipe instead of to the sewer, or letting the drip go to the 
atmosphere, is that a vacuum cannot be maintained if the cylinder is thus 
placed in communication with atmospheric pressure. 

In the Sturtevant compound engine there are two drainage systems : one 
for the cylinders, as briefly mentioned above, and another for draining water 
of condensation from the stuffing boxes. As shown in Fig. 139, small pipes 
connect with the depressions at the valve rod and watershed partition stuff- 
ing boxes. The condensation collecting at these points is led through the 
piping, which is wholly within the inclosing frame, and delivered to the- 
sewer. The rest of the piping within the frame is the system of forced 
lubrication, by which all bearings and sliding surfaces are supplied auto- 
matically with lubricant. 

To start the engine, if condensing, the air and circulating pumps are 
first put into operation so that a partial vacuum will be created in the con- 
denser. Meanwhile, a little steam should be allowed to warm the cylinders, 
the condensation leaving by the cylinder drainage system. 

As soon as convenient the indicator should be attached, for the valve 
setting is not yet final. Fig. 148 shows the indicator rig. The indi- 
cators are located at the three-way cocks A and B, which allow steam to 
enter, the indicators from the two ends of the cylinders. The reducing 
motion consists of a rod R, moving vertically in a projection on the 
door, and a rocker K, which transmits the crosshead motion to the rod 
R, the free end D of the rocker engaging the rod R at C. As shown 
at the right-hand side of Fig. 10, the rod R is directly below the indi- 
cator cord. 

When a moderate speed has been attained, diagrams should be taken 
simultaneously from the cylinders and carefully examined for defects in 
valve setting. The adjustments to be made depend, of course, upon the 
faults revealed, but usually slight adjustments in the lengths of the valve 
stems will be sufficient. For instance, suppose the top of the high-pressure* 
cylinder is developing more power than the bottom, the card areas may 
be made nearly equal by shortening the high-pressure valve stem, which 
will bring cut-off earlier at the top and later at the bottom; the leads 
will change but little, that at the top decreasing, and that at the bottom 
increasing. The same principles apply to the low-pressure side, but in 
general the low-pressure valve will give satisfactory distribution if it 
was carefully set during erection aud the high-pressure valve is properly 
adjusted. 



THE STURTEVANT COMPOUND ENGINE 143 

Adjusting the Governor 

The only remaining adjustments are those pertaining to the governor. 
As already stated, this engine is regulated by a modified form of the Kites 
inertia governor, which has been so universally adopted for high-speed en- 
gines that a description is unnecessary. It is well, however, to bear in 
mind a few of its fundamental principles, for governor adjustments call 
for a knowledge of these principles rather than a blind following of direc- 
tions for changing certain adjustments because of certain defects. 

The governor combines both the centrifugal and inertia effects : the for- 
mer controlling the speed variations caused by changes of load, while the 
latter has to do with steadiness. The governor arm tends to maintain its 
rotative speed due to the inertia of the heavy weights. If the load increases, 
the engine tends to slow down, that is, the rim of the governor wheel will 
slow down but the weights tend to move at the same speed as before. The 
effect of these two movements is that the center of gravity of the arm 
moves inward, increasing the load and lengthening the cut-off. 

If while the load changes slightly the speed is steady, but lower than 
desired, the tension of the governor spring may be increased, or the spring 
pin P moved outward. If on increase of load, the speed drops more than 
it should, the spring pin P (Fig. 146) may be set nearer the governor arm 
pivot by moving it along the slot, or the weight at 17 ma}^ be reduced, and 
also the tension in the spring. In short, speed regulation consists primarily 
in balancing the spring tension against the centrifugal force of the arm. 
Exact balance at all points in its movement would result in practically 
uniform speed from no load to full load, but the governor would then lack 
stability, hence it is better to not quite balance the centrifugal force, so 
that the speed will drop about 2 per cent, with an increase from no load to 
full load. 

If the governor is unsteady, and requires several long swings of the arm 
to correct the speed, weight may be added to the long end of the arm [M, 
Fig. 146), or the spring pin P may be moved outward in its slot. 

These brief remarks regarding the governor are for testing plate adjust- 
ments, but it is assumed that the valves are correctly designed, the pins 
of ample size, and properly lubricated. After long service wear may affect 
the condition of the parts that were all that could be desired when on the 
testing plate. When in poor condition, governor adjustments may be 
slightly different, for a worn valve, scored pin, or insufficient lubrication 
may be the fault of poor speed regulation. 

The instructions given for setting the valves refer to the Sturtevant com- 
pound engine having cylinders 10 and 18 ins. in diameter, and a stroke of 
10 ins. This type of engine is built in other sizes, as given in the table 
on page 144. The various sizes of this class of engine vary in dimen- 



144 



VALVE SETTING 



Details and Measurements op Sturtevant Compound Engines 







High-Pressube Valve 


Low-Pressure Valve 




"a 




Laps 




Leads 


s 


.^"o 

0?^ 


S 
o 


"a! 
> 

H 




Laps 


Leads 




















O o 
















o 

o 

pq 

3 












a 
1 



ffl 

s 






Size 


OF Engine 


> 
B 




s 

5 




o 
« 

o 
02 


1 
1 


ft 


O 
O 


11 


s ^ 


-2 =^ 

«^ 

^ o 




> 

> 

B 

s 

i 


o 
H 

S 
oi 


s 

o 
o 

m 
i 


ft 

O 

§ 
ca 

H 




S 
o 

o 
pq 






g 









1 


s 
3"2- 


5 
3¥ 


H 


H 


S 








3'. 


fe- 




6i- 


lOi X 61 


2| 


H 


U 


If 


2U 


4| 


Oi 


it 


if 





A 


*7 _ 


12 X 7 


2i 


i 


7 
















2-J- 














8 - 


14 X 8 


3-,% 


1 


i 


^ 


i 


A 


^ 


2A 


21 


5A 


3| 


1-^2 


13^ 





i 


A 


A- 


10 - 


18 XIO 


4| 


ll 


H 


l\ 


1 
4 


1 

4 


i 


2-,^ 


3i 


511 


4| 


n 


If 





« 


^^ 


i 



* Valves being redesigned. 



sions only, therefore the valves are set in the same manner for all, the 
measurements differing of course 
and important measurements. 



The above table gives further details 



XV 



THE EICE AND SAEGENT ENGINE 

This engine, as shown by the cut given herewith, is of the heavy-duty 
CorHss type, primarily designed for direct-connected electrical work and 
for operation at speeds somewhat higher than the ordinary Corliss engine. 
The motions of all the valve parts are obtained without wrist plates, are 




FIG. 149. 



made as short as advisable, and all parts made very strong with unusually 
large wearing surfaces. The illustration (Fig. 149) represents a small, 
simple engine. The company also builds compound engines of both tan- 
dem and cross types and vertical engines of large sizes; the sizes ranging 
from 150 horse power to 2,000 horse power on single cylinder engines and 
250 to 7,500 horse power or larger on compound engines. Engines of 1,000 
horse-power rated load are regularly operated at 150 revolutions and 
smaller engines at suitable slightly higher speeds. Engines of the largest 
size are run as slow as 75 revolutions. 

145 



146 



VALVE SETTING 



Illustrations are shown herewith of the inlet and exhaust valve gears. 
The operation of the inlet valve gear is as follows : 

Fig. 150 shows the inlet valve gear for the front end of the cylinder 
in its extreme left and opening position. The latch A on the valve-stem 
lever B is in the position of engagement with the toe C on the rocker D. 
The pin E connects through the intermediate rockers and rods with the 
steam eccentric on the engine shaft^, and the pin F connects to a similar 
inlet gear at the back end of the cylinder. As the rocker D moves to the 
right, the toe C engages the latch A, moving the inlet valve to open, and 
raising the dashpot plunger which is connected to the pin P. Cut-off is 
accomplished by the toe C turning downward on its pivot spindle H to 
release the latch A. The spindle H has a cam lever / rigidly attached in 




FIG. 150. 



FICx. 151. 



the rear, which in turn is carried between two rolls, J J. These rolls 
turn on pins in the cut-off lever K, which latter turns freely on the valve- 
stem journal. The arm L above forming part of the same casting as the 
cut-off lever K, is connected to the governor by the rod M. This rod is 
held firmly by the governor and does not move unless there is a change 
in the speed of the engine. The rod N connects to the valve gear at 
the head end of the cylinder. The latch A is released at some point 
in the opening movement of the rocker D, toward the right. This is ac- 
complished when the rise of the cam lever passes between the cam 
rolls J J. It is obvious that the amount of valve opening and the length 
of cut-off depend on the position of the cut-off lever K, as controlled by 
the governor. The further to the left the lever K, the earlier the cut-off. 



THE RICE AND SARGENT ENGINE 



147 



Fig. 151 shows the rocker D at the extreme right of its motion. Re- 
lease has taken place and the valve is about to be closed by the pull of the 
dai^hpot. The valve then closes promptly and the lever B turns to the 
position shown in Fig. 150. The cut-off lever A' is here shown in the 
position giving nearly the latest cut-off, which is about three-quarter stroke 
of the piston. On the return movement of the rocker D, the cam rolls 
J J raise the cam lever / and the toe C to the engaging position. At the 
latter part of the movement of the rocker D to the left, as the toe C 
2)asses under the latch A, the latter is raised by the toe sufficiently to clear 
the same and the latch then drops by gravity in front of the toe to the 
engaging position, as shown in Fig. 150. 

On the exhaust gear the motion of the eccentric is transmitted through 
the intermediate rockers and rods to the bell crank shown in the illustra- 
tion Fig. 153. The motion of the bell crank is transmitted to the exhaust 




FIG. 152. 



lever through a link, thus allowing the valve to pause at the end of a stroke. 
The valves of the engines are set as follows : 

Before setting the valves, see that the lengths of all valve-gear rods and 
clutch rods are so adjusted that all the valve rockers and intermediate 
rockers are plumb. These are the rockers shown in the illustration of the 
complete engine herewith, to which the eccentric rods and the valve-gear 
rods are attached. When these rockers are plumb, rotate the eccentrics on 
the shaft and adjust the eccentric rod until the travel of the intermediate 
rockers on each side of the plumb line is equal. Then place the engine on 
the forward center and make coinciding marks on the crosshead shoe and 
the slide. Then move the engine backward, so that these lines will be 
^-in. to ^g--in. apart. This will give from ^L- -in. to ^-in. valve opening 
at the time the engine passes the center. Then rotate the steam eccentric 
on the shaft, so that the valve and port will be line and line and moving 



148 



VALVE SETTING 



to open the valve. The arrangement of the valves in the cylinder is as 
shown by Fig. 153. 

To set the exhaust valves, move the engine back about 3^ ins. and 
set the eccentric so that the valve and ports are line and line and moving 
to close the proper valve. Then turn the engine to the back center and 
repeat this operation, only turn the engine back more than 3-| ins., and 
then approach the marks as in the regular operation of the engine, so 
as to get out all back lash. 

This distance of 3^ ins. should be varied through quite wide limits 
to give more or less compression according to the speed of revolution of 




FIG. 153. 



the engine and according to the method of operation, whether condensing 
or noncondensing. 

If the marks do not come exactly the same as at the front end, adjust 
the eccentric rod to make up one half of the difference and move the 
eccentric so that the lines on the valve and ports again come together. 
The whole setting should now be repeated. 

At all times have the length of the rod connecting the two rocker 
levers of such length that both levers will be plumb at the same time. 

On the low-pressure side the steam valve should be set to open about 
f of an inch from the end of the stroke, and the exhaust valves close from 
6 to 8 ins. from the end of the stroke. 

On tandem-compound engines, a mark should be made on the front end 
of the high-pressure sole-plate clamp when the engine is cold; then when 
the engine is thoroughly heated, measure the amount the high-pressure 
cylinder has moved due to the heat expansion, and lengthen out the long 



THE RICE AND SARGENT ENGINE 



149 



clutch rods the same amount. The valve adjustment will then be prac- 
tically the same as if the valves were set with the engine hot. 

The steel plates on the latches and toes should lap by each other when 
engaged, ^ in. on cylinders up to 23 ins. diameter, -^^ in. on cylinders 
from 24 ins. to and including 30 ins. and -^ in. on cylinders above 30 ins. 
diameter. The distance the latch and toe plates move by each other before 
engaging is adjusted by the dashpot rod, and should be kept as small as 
practicable. On the smaller size cylinders this amount should not be 
less than -^ in. and should not exceed ^ in, on the largest size. 

Adjusting the Eites Inertia Governor used on Rice and Sargent 

Engines 

The details of this governor are as shown by the cut given herewith 
(Fig. 154). This illustration shows the governor in the shop set on wooden 



G K H 




FIG. 154. 



blocks merel}'' for the purpose of photographing. Its position on the 
engine is shown in Fig. 149. The operation of the governor is as follows : 
The governor weights are caused to revolve by means of a belt acting 
on the pulley shown at A. The circular weights shoAvn at B and C are 
suspended on pivots shown at R. These weights, due to the centrifugal 
force, tend to fly from the center and are held from flying too readily 
by means of the spring D. These weights are connected with the bell 
crank E by means of the arm F and the similar arm which is out of sight 
connecting the weight C. The action of the weights on the rocker E is 
as shown by the sketch given above the cut, the points G and H repre- 



150 VALVE SETTING 

senting the connection of the arms F with the weights B and C. The 
points G and H are compelled to move in a straight line, since the revolv- 
ing weights throw directly from the center. Therefore it 'is seen that 
when the points G and H separate, moving toward L and L', the point 
E', which represents the pivot at the end of the rocker E, is compelled to 
move toward the point M, and when the weights, due to a slackening in 
speed, approach the center and the points G and H approach the point K, it 
is seen that the j^oint E' would move toward point M'. This rocker E is 
rigidly connected to the shaft ^S', and the motion of the weights B and G 
imparts an oscillating motion to the shaft ;S' which is transmitted by means 
of the mechanism T to the lever N, the end of which has a motion in an 
arc of a circle toward N' and N" . The governor rod connecting with the 
cam collar, which determines the point of cut-off, is connected at this 
point N. A retarding dashpot to prevent the governor being too sensitive 
is connected at the point F. 

All parts of the governor should work freely and all cut-off connections 
should have an appreciable endwise movement on their pins. 

The governor cross shaft must be perfectly free to move. The governor 
may be made more sensitive by screwing one or both of the plugs out of 
the spring, and less sensitive by screwing these plugs into the spring. 
One-half turn of one plug is sufficient for a trial. This operation neces- 
sitates removing the spring from the governor and securing it in a vise. 

To cause the engine to run faster, increase the tension of the spring 
by turning the spring on its screws. To cause the engine to run slower, 
reverse this operation. One turn of the spring will usually make a dif- 
ference in speed of about one revolution of the engine. 

Adjusting the Cut-off Eods of the'Eice and Sargent Engine 

In adjusting the cut-off rods on the high-pressure side of a compound 
engine, or on a simple engine, the cam slot on the governor is so designed 
that with the governor blocked at the top or the bottom of this slot, the 
position of the cam collar on the valve bonnet will be the same. There- 
fore block the governor at either the top or the bottom of this slot and 
adjust the rod leading to the forward governor rocker so that the latch 
and toe will just miss connecting. Then adjust the governor rod be- 
tween the front bonnet and back bonnet so that the back-end latch and 
toe will just miss. This method of adjustment will give the greatest 
obtainable range of cut-off and still make certain that no steam will be 
admitted to the high-pressure cylinder when the governor is clear up or 
clear down. 

To adjust the low-pressure cut-off rods, first equalize the cut-off on 
the front and back ends bv means of the cut-off rod between the front 



THE RICE AND SARGENT ENGINE 151 

and back bonnets. Then adjust the cut-off rod loading from the gov- 
ernor cross shaft so as to get the desired receiver pressure. 

On condensing compound engines a receiver pressure of 10 to 15 lbs. 
is desirable, with an initial steam pressure of 100 to 150 lbs. On non- 
condensing compound engines with the same initial i^wessure, the receiver 
pressure should be 36 to 40 lbs. 

The low-pressure cut-off should ahvays be so adjusted as to allow the 
low-pressure steam valves to open slightl}^, when the governor allows the 
toe and latch to pass each other on the high-pressure side. This adjust- 
ment is made after the proper receiver pressure is obtained, and will pre- 
vent racing on light loads and in process of preparing to throw the load 
on the engine. 



XVI 



EEYNOLDS (1890) AND GIEDER FEAME COELISS ENGINES 

The steam valves of these engines admit the steam under the valve 
edges nearest the center of the cylinder and while the valve is traveling 
away from the center. In common parlance, they admit the steam " un- 
der." The steam edge of the cylinder port is also located nearest the center. 
The steam edge of the steam port and that of the valve are shown in Fig. 




155, at A and A'. Logically, the steam exhausts over the edges of the 
exhaust valve and port nearest the cylinder center; these edges are shown 
at B and B', Eig. 155. In the figures the direction of travel of both 
valves when opening is indicated by arrows. 

The direction of travel of the wrist plate when the crank-end steam 
valve is opening and the crank-end exhaust valve is closing is shown by 
the arrow on the wrist plate. (At the same time the head-end steam valve 
has closed and the exhaust valve is open.) 

152 



REYNOLDS (1890) AND GIRDER FRAME CORLISS ENGINES 153 

The working edges of the valves and ports are shown by radial lines on 
the valve end and steam-chest end, when the back bonnets on the side of 
the cylinder opposite to the wrist-plate side are off. The steam and ex- 




haust valves both indicate lap when the lines on the valves are nearer the 
center of the cylinder than are the lines on the chest. This condition is 
shown in Fig. 157, which represents the end of one steam valve and chest 




FIG. 157. 



with the back bonnet off. The line A on the valve overlaps the line B 
on the steam chest toward the center of the cylinder. 



154 



VALVE SETTING 



Fig. 165 shows the wrist-plate central for adjusting the valve connec- 
tions. There are three marks on the back of the wrist-plate hub and one 
mark on the wrist-plate stand, which is bolted to the cylinder, the marks 
appearing as in Fig. 158, When the lines 2 and ^ come together the wrist 
plate is central; when 1 and Jf. are opposite each other the -W^ist plate is 



LU"- 


4 


-UJ^ 




: 


2 Jl 






FIG. 158. 

on one extreme of its travel, and when 3 and Jf are opposite each other the 
wrist plate has reached its other extreme. 

To set the valves as in Fig. 155, first even up the travel of the rocker 
arm and wrist plate, according to the instructions for setting Corliss valves, 
in Chapter V, and then, placing the wrist plate in its central position, pro- 
ceed to adjust the valve rods so the steam and exhaust valves will have the 
lap given opposite thfe cylinder diameter in the accompanying table. Set 
the engine on the center and move the eccentric until the steam valves have 
the lead given in the table. 

To Adjust the Length of the Dashpot Eods 



Eef erring to Fig. 159, when rod H is down as far it will go, the 
shoulder E on the brass hook should just clear the steel block F on the 
valve arm, as shown, leaving clearance below the' block, as at 0. This 



REYNOLDS (1890) AND GIRDER FRAME CORLISS ENGINES 155 
Table of Laps and Lead for Setting Valves 



Diameter of Cylinder 


Lap of Steam Valves 


Lap of Exhaust Valves 


Lead of Steam Valves 


8 


A 


A' 


3:4 


10 


A 


l\ 


-3^ 


12 


-?6 


1^ 


.^ 


14 


i 


i 


^ 


16 


i 


i 


.V 


18 


i 


^ 


3^. 


20 


i 


i 


^ 


22 


A 


l^ff 


A 


24 


iV 


A 


A 


26 


a\ 


A 


A 


28 


A 


-^ 


6^ 


30 


-h 


-:\ 


A 


32 


1 


i 


-A- 


34 


1 


i 


^S 


36 


i 


i 


A- 



adjustment of the rod H must be made Avlien the wrist plate is at its ex- 
treme throw, as shown by a mark on the back hub. 




FIG. 159. 



156 



VALVE SETTING 



Heavy Duty and " Eeliance " Types 

Figs. 160 and 161 are views of the C3dinders on these types of engine 
which are built by the same company. In design these engines differ from 




those illustrated in Figs. 155 and 156 in having less heavy wrist plates to 
suit higher engine speeds, and in being equipped with double-ported steam 
and exhaust valves. 




I I 

FIG. 161. — RIGHT-HAND SIDE. 



REYNOLDS (1890) AND GIRDER FRAME CORLISS ENGINES 157 

Fig. IGO shows the wrist plate in its central position, with the valves 
lapped. The steam is admitted over and through the valves, the steam 
edges of the steam valves being shown at A and the working edges of the 
two ports — i.e., the edges away from the center of the cylinder at A'. The 
exhaust edges of the exhaust valves and ports are those nearest. the cylinder 
centers, and are designated respectively B and B'. The arrows show the 
direction of travel of the valves when opening. 

When the back bonnets of these valve chests are removed, two lines 
will be found on the valves and two on the chests, marking the locations 
of the two port edges on each. The steam valves are thereby known to be 
lapped when the lines on the valves are farther from the center of the 
cylinder than the lines on the chest, and the exhaust valves lap when the 




FIG. 162. — LEFT-HAND SIDE. 



lines on the valves are nearer the center of the cylinder than the lines on 
the chest. 

To set these valves, proceed as in Figs. 155 and 156, with the exception 
of providing the lap for the steam valves in the manner just stated. Allow 
the amounts of lap and lead given in the table already referred to, which 
is applicable to both types of valve. 

Fig. 161 shows the position of the wrist plate when the engine is on 
the center and the eccentric is advanced to give the steam valves proper 
lead. The adjustment of the dashpot rods is obtained in the manner de- 
scribed in the preceding section of this chapter. 

Fig. 162 shows the valve-gear side of one of these engines, by which it 
will be seen that the rocker-arm motion is direct ; this implies that the 
eccentric should be advanced ahead of the crank in the direction of 
rotation. 



XVII 
THE WRIGHT STEAM ENGINE 

Wright engines were designed and built by the late William Wright 
and many of them are still in use throughout the country. During the 
many years of his activity in the engine field, Mr. Wright designed a num- 
ber of different types of valve and valve motion for his steam engines. In 
the rotary-valve engines there were several modifications in the driving 
mechanism and of the flat or gridiron valves there were several different 
shapes of valve and port, but in the latter case the driving mechanisms 
were all practically the same in detail and principle. As there are a large 
number of Wright engines in daily operation, an explanation of the setting 
of the gridiron valve should prove of general interest. 

Figs. 163 and 164 give views of the steam and exhaust sides, respec- 
tively, of a Wright automatic cut-off engine with four gridiron valves direct- 
driven from one eccentric. In both these figures the eccentric is indicated 
by A^ and the eccentric-rod is shown at B^ Fig. 164. The rock-shaft D D' 
extends under the engine frame from side to side, and on each end of the 
shaft are shovm. the rocker arms. In Fig. 163, E represents the hook-rod; 
F, the steam wrist plate; G G, the steam valve rods; H H, the steam 
valve cranks ; / I, the steam valve stems and yokes, and J J are the steam 
chest covers. The same parts relating to the exhaust are indicated by the 
same letters primed. 

Valves and Valve Movement 

Eegulation is effected b}^ a pendulum governor, which is shown in 
the two illustrations just referred to. When the governor is in operation, 
the balls revolve around the central axis, and as they rise, lift the vertical 
rod a, the lower end of which is shown at &^ Fig. 164, where it is attached 
to the arm c which actiiates the rock shaft d. To this shaft are attached 
the arms e e, which draw the splined spindle through the hollow rock shaft. 

Both the steam and exhaust valves work vertically and are actuated 
by valve stems extending downward through stuffing boxes in the bottoms 
of the chests. The steam and exhaust wrist plates are keyed to one shaft, 
which extends under the cylinder from one side to the other, so that they 
operate at the same time, when motion is imparted by the hook rod E. 

159 



THE WRIGHT STEAM ENGINE 



161 






The two shafts which carry the valve cranks are hollow and stationary, 
each having one steam and one exhaust crank on their respective ends. 
The main steam valve stems are fastened into the yokes with set screws, 
and on their lower ends the yokes are provided with dash pots, which also 
act as guides. The yokes are operated by steel slides which are fitted into 
the hollow valve crank and act on the toes held in the yoke. In the ex- 
haust valve yokes are provided sliding blocks to which the valve cranks 
are secured by a pin, the block allowing the pin center to change its posi- 
tion horizontally as it moves vertically. 

Of the four gridiron valves with which the Wright engines are pro- 
vided, two steam and tAvo exhaust valves, one of each is placed on one side 
of the cylinder and a similar pair on the opposite side. The steam valves 
are V-shaped and partly balanced, 
the valve seats being separate and 
bolted to the cylinders. In Fig. 165 
the steam valve as shown at a a and 
& h indicates the seat over which the 
valve rides, permitting the steam to 
pass from the chest through the 
valve and seat into the cylinder. The 
exhaust valves are shown at c c, Fig. 
165, and the seat at d with a plate e e 
to hold the valve against the seat. 

A study of Fig. 166 will give 
an idea of the arrangement of the 

valves in the cylinder. In the plan one end of the cylinder is in cross 
section, showing the steam and exhaust valves for that end in their relative 
positions. The elevation shows the steam valve chest with the valve in 
position, the small letters having the same significance as in Fig. 165. 
In Fig. 166 it will be seen that A is the steam passage to the valves and 
B the exhaust passage away from the cylinder, but to understand more 
fully the arrangement of the mechanism for driving the valves, reference 
should be made to Fig. 167, in which A is the elevation of the steam 
wrist plate and B a plan view. At F the wrist plate is in its central posi- 
tion, with the cranks H II and the yokes / 7 in the same relative positions. 
On one end the yoke is shown in section and the manner in which the steel 
slide a engages the steel toe & in the yoke is also indicated. 

When the wrist plate is in the position indicated in Fig. 167, the other 
valve-rod pins are in the positions shown, and when the wrist pin is at c 
at one extreme of its throw, the other valve-rod pins are at c^, c^ c^ and c*^ 
respectively. By the time the wrist pin has reached its other extreme of 
travel at d, the other pins are at d^j d-, d^ and d*. In the plan B, Fig. 167, 
is shown the rock shafts e e with the steam valve crank H in place on only 




FIG. 165. 



162 



VALVE SETTING 



one of the shafts. The sj)lined spindles / / pass through the hollow rock 
shafts and valve cranks as shown^ and on one end is a nut g which can 
be adjusted to lengthen or shorten the spindles. At h is shown the key 
which is set diagonally across the end of the spindle and engages a key- 
way in the plate a. A sectional elevation through the same spindle and 



l ^s>yS:>SNxV>XNVS>^^c<-^^N>X>^^^^ 




/■ -. ^ 



3 



v//y///////////^^^^^^^^z^ 



V, 




Elevation 
FIG. 166. 




shaft is shown at C, and at i is a bracket which helps support the rock 
shaft fc. 

Fig. 168 illustrates the exhaust wrist plate F' , which is on the same 
shaft, only at the end opposite to that occupied by the steam wrist plate. 
It will be noted that the valve-rod pins in the wrist plate are set above 
the center of the plate, while those in the steam wrist plate are on the same 



THE WRIGHT STEAM ENGINE 



163 



line when set central. As seen in Fig. 1G8, the valve crank //' is fastened 
to the valve yoke I' by a pin in the sliding block a. 




FIG. 167. 



Both the steam and exhaust valves are lapped when they are down at 
the lower end of their travel, with the plunger in the dash pot seated. 



164 



VALVE SETTING 



When traveling up the valves open, and close in coming down, but to get 
a complete understanding of the movement of each valve, reference should 
be made to Figs. 169-172, which have uniform reference letters. The valve 
is shown from one side, but this must not be mistaken for the true relative 
position of the valve to the valve gear. One steam valve is shown only. 

In Fig. 169 * the wrist plate F, valve crank //, yoke / and valve a are in 
the position at which the valve is lapped, and the wrist plate and eccentric 
are on the center of their travels. The center line A A \?> horizontal 
through the wrist plate and valve-crank rockers, B B representing the cen- 
ter of the wrist plate and G C the center line of the valve-crank shaft. The 




FIG. 169. 



dotted line D D shows the arc in which the end of the plate d travels when 
the valve admits steam during the full stroke, and to the right of Fig. 169 
is the eccentric circle in which X, X^, X^ and X^ are separate eccentric 
positions, and C and C" are two separate positions for the crank. The 
arrows denote the directions of travel of each part at this central position 
of the eccentric and wrist plate.. 

Bearing in mind that the wrist plate on the opposite side is operating 
the exhaust valve, it will be noted that when the steam wrist plate and 
valve crank are in the position shown, connected by the rod along the 
line G, the wrist-plate pin and valve-crank pins for the exhaust on the 

*In Figs. 169-172 the plate at the bottom of the valve yoke I is not shown as a 
swinging plate, on account of the small scale of the drawing. It is correctly given on 
page 169. 



THE WRIGHT STEAM ENGINE 



165 



opposite end are at c c connected along the dotted line G'. When the wrist 
plate and valve crank are in the position shown, with the valve lapped 
and the crank at its center C on the eccentric circle, the eccentric will 
be at X. Since the valve opens while traveling up, all the parts must 
move in the direction denoted by the arrows. To overcome the lap, the 
eccentric would be moved up to X^, and then to give lead the eccentric 
must be still further advanced to X-, with the crank still at C. This 
gives the angle at which the eccentric should follow the crank, and if 
continued together in their travel to the point of cut-off, with the plate d 
at its maximum cut-off position, the crank and eccentric would be at 



Port Opening 




0* and X^, respectively, or the crank would have reached 90 per cent, 
of its stroke. 

It will be noted that the movement of the eccentric is enough to give 
a travel twice the width of the port and lap of the valve, but that the 
valves themselves travel only far enough to overcome the lap and port 
opening. The full lines show the valve port and the dotted lines the 
position of the port in the valve seat. The dotted lines to the side give 
the relative positions of the valve and port in port opening and lap, and 
the dotted lines to the side of the valve yoke I show the positions to 
which the plate d must lift the yoke to overcome lap and give full open- 
ing. The sum of the two is the valve travel. 

Bearing in mind that the eccentric is at X, with the wrist plate, valve 
crank and valve in the positions shown, we may advance one step in the 
movement. In Fig. 170 the position of the wrist plate, valve crank and 



166 



VALVE SETTING 



valve are shown when the eccentric is advanced to the point X on the 
travel to give lead to the valve with the crank on its center C. The crank 



Poit Opening 




and eccentric will now travel together. The relative positions of the 
exhaust pins are shown at c c. 

Fig. 171 shows the valve fully, opened, having reached the full height 



,-^- 




FIG. 172. 



THE WRIGHT STEAM ENGINE 



167 



of its travel. The eccentric and wrist plate are also at the extremes of 
their travels, and as the plate d is so far extended under the valve yoke 
that it will not disengage, the valve will not close until the crank and 
eccentric have so far advanced in their travels as to allow the valve to be 
lowered far enough to effect cut-off, which is shown in Fig. 172. In this 
iigure it will be noted that the direction of travel in the wrist plate, valve 
crank and valve have been changed, and cut-off has been accomplished. 

As shown in Fig. 167, the governor acts on the steam valves and 
effects an early or late cut-off through the medium of a splined rod run- 
ning through the valve-crank shafts ; 
when the rod is drawn through the 
hollow valve crank, it either causes 
the plate not to pick up the valve 
yoke at all, or allows it to carry full 
stroke. A study of Figs. 174, 175, 
and 176 will fully explain this 
action. In these figures A A is 
the center line of plate d and valve 
yoke /. The end of the rod is 
shown at 8. The bottom drawings 
are plans and those at the top are 
elevation views. 

In Fig. 17-4 it will be noted that 
the splined end of the rod is ex- 
tended through as far as it will go, 
thus making the plate d extend 
through the valve yoke to its posi- 
tion for maximum throw. In the 
elevation the line D D shows the 
arc through which the end of this 
plate will travel while operating the 
valves. When the conditions are as 
shown in Fig. 173, the governor 
should be at rest or at its lowest 
point of operation. The rod S will 
then be ready to travel in the direc- 
tion of the arrow when the gov- 
ernor takes hold. When the valve gear is in the position shown in Figs. 
169, 170, 171, and 172 the rod S and plate d are as shown in Fig. 174. 

With conditions as in Fig. 174, the valve is given its full maximum 
travel, but from that point, as the governor begins to pull the rod 8 in 
the direction of the arrows, the plate d travels in the arc of circles which 
grow smaller and smaller until the position shown in Fig. 175 is reached. 




FIG. 173. 



168 VALVE SETTING 

Here it is shown that the rod S has been drawn out to half the distance 
of the length of the splined end, and as a consequence the plate d has 
been drawn back until the arc D D through which that end travels has 
grown smaller and does not lift the valve so far. The difference in the 
distance to which the plate now raises the valve, and the distance required 
for full port opening is shown at / and g, the latter reference letter in 
this case equaling the full valve travel. The eccentric, always moving the 
same amount, throws the plate d along the line D D enough farther to 
allow it to disengage itself from the yoke I, and the latter in dropping 
causes the valve to cut off. This event occurs when the piston has traveled 
about one fifth of its stroke, with the rod and plate in the positions shown 
in Fig 175. 

When the governor weights have reached their maximum position and 
the engine its normal speed, the splined rod is drawn out still farther 
until the plate d, Fig. 176, will not engage or pick up the valve at all. 
At this point, when no steam is admitted to the cylinder the minimum 
valve travel has been reached. 

Setting the Valves 

It will be noted that the valve stems set down in the valve yokes on 
a shoulder and are secured in place by a set screw. This does not allow 
of easy adjustment of the length of the valve stem or valve lap, and owing 
to the fact that the valve stems are not easily adjustable, more care must 
be taken in each step toward setting the valves. 

First, place the wrist plate in its central position, as shown in Figs. 
167 or 169, and note that the hook pin at the top of the steam wrist 
plate is not on the vertical center line of the plate, but is off center a few 
degrees in the direction of the cylinder head or away from the engine 
shaft. The two steam valve-rod pins on the wrist plate are on the same 
center line as the wrist-plate center, and when these pins are level and on 
an exact line with the wrist plate and valve-crank centers, the wrist plate 
is on the center of its travel. It is a good plan to clamp the wrist plate 
into central position, while doing the first part of the valve setting, by 
slacking off on the washer on the end of the stud, placing paper under- 
neath and clamping down on that. If the wrist plate is keyed on the 
shaft, it can be held in place with a thin wedge driven between the boss 
of the wrist plate and the cap of the bearing next to it. 

Then adjust the length of the valve rods so that the plate d in the 
valve crank H is horizontal, as in Fig. 169. If there is no adjustment 
in the length of the valve rods, then note whether or not the valve cranks 
are in the required position when the wrist plate is central. In all prob- 
ability they will be, but, if not, the valve rods must be changed to the 



THE WRIGHT STEAM ENGINE 



169 



U- M- .^1 




170 VALVE SETTING 

proper length, even if they have to be taken to a machine shop for the 
purpose. With the gpvernor in its lowest position, adjust the length of 
the rod 8 so that it is at its outer extreme position, as in Fig. 17-i, with 
the plate d as shown here and in Figs. 169, 170, 171 and 172. Now 
hook up the eccentric rod to the wrist plate and free the latter so that it 
will work and roll the eccentric slowly around the shaft in the direction 
it is to run. Carefully note the length of travel of each of the valves 
and see that when they are at the top extreme of their travel that the 
ports are open no more than in Fig. 171. If both the valves have the 
same travel and should pass over the edge of the port or farther than 
necessary to give a full port opening, the plate d may be extended too 
far, and as a remedy the rod ;S^ should be shortened so that the valve 
can be raised just far enough to give the full port opening. If the 
two valves travel unevenly they must be adjusted to travel alike, and 
separate adjustment can, of course, be made to each. If the valves do 
not travel far enough to give a full port opening with the adjustment 
of plate d as in Fig. 173, then something must he. done to lengthen the 
valve stems. 

After the steam valves have been adjusted the next thing to do is to 
set the exhaust valves so that they will travel just far enough to give a full 
port opening. When turning the eccentric around with the wrist plate 
hooked up, a mark can be placed on the wrist plate and another mark 
opposite it, at each extreme of the travel, on the hub, adjacent bearing 
cap or washer, as the case may be. With dividers, the distance between 
these points can be bisected and a mark made to center the wrist plate. 
If, when the mark on the wrist plate is brought to this center mark, it 
does not appear central, as in Fig. 169, then the length of the eccentric 
rod is wrong and must be proven. The best way to do this would be to 
make a new set of marks, first placing the wrist plate central, as in Fig. 
169. Then make a central mark on both wrist plate and adjacent cap and 
lay out the two extreme points as follows : 

In Fig. 173 let A B he the distance from the center of the wrist-plate 
hub to the center of the hook pin, A C the distance from the wrist-plate 
hub center to the surface of the hub or washer where the marks are to 
be, D E the travel of the hook pin and F G the distance apart the extreme 
positions are to be. 

For example, let A B = 10 ins., A C = 3 ins., D E ^ 5 ins., and 
F G= ? Then 

10: 3:: 5:? 
(3X5)-M0 = 1.5 ins. 

In this case the distance between the extreme points would be 1-J ins., 
and taking a pair of dividers and setting them at f in., a mark could 



THE WRIGHT STEAM ENGINE 171 

be scribed on each side of the center line with which the center line on 
the hub should coincide at each extreme of the travel. Turn the eccentric 
around again and if the center mark on the hub comes short of one mark 
and over the other, one of the rods is too long or too short between the 
eccentric and the wrist plate. 

Note whether or not the rocker arm travels equally on each side of the 
center line, which should be exactly vertical when the eccentric is at half 
stroke. If the rocker arm does not travel equally on each side of the 
center line, as for illustration from D to B and B to E in Fig. 176, the 
eccentric rod is too long or too short and must be adjusted. If the travel 
of the rocker arm is correct and still the wrist plate does not travel equally 
to its extreme positions, the hook rod needs adjustment. 

Having equalized the travel of the wrist plate and valves, proceed to 
set the valves for running. Place the engine on one center and pull the 
eccentric around until there is lead on the steam valve for that end, and 
then make the ccentric fast to the shaft. Next pull the engine around 
and observe that the exhaust valves release at from 90 to 95 per cent, 
of the stroke and that the steam valves cut off at from 80 to 90 per cent, 
of the stroke for the maximum. The exhaust valves should close for 
compression at from 95 to 97 per cent, of the stroke. Make the lead of 
the steam valves nearly equal with a trifle more on the crank end. 

After the valves are set, block up the governor to its highest point, 
and while pulling the engine around one complete revolution, see that 
fhe steam valves do not pick up at all. To reverse the engine, reverse the 
eccentric. If, when the indicator is applied, it is found that earlier valve 
action is desired, it is best to set the eccentric ahead, or back if later 
action is desired. To get an earlier steam cut-off, the change can be made 
on the rod 8, Figs. 174, 175 and 176, but if earlier cut-off is secured 
in this way, there will be less lead. To obtain a later cut-off in this way 
will give more lead. 



XVIII 
THE EEYNOLDS LONG-EANGE CUT-OFE 

To operating engineers in general the Eeynolds long-range cut-off as 
manufactured by the Allis- Chalmers Co. is not very well known. On 
the surface there appears to be nothing out of the ordinary in the valve 
gear that would distinguish a Eeynolds from any other Corliss engine, 
but upon cK)ser inspection some essential features will be found so rad- 
ically different that they will cause the uninitiated considerable trouble 
until the movement is understood, after which the valve gear is simplicity 
itself. The long-range cut-off is designed to give a maximum cut-off for 
power, and the essential feature of the steam valves is that they have a 
negative lap or opening when in mid position, the cut-off being made 
entirely by the governor through the knock-off cam. 

In the first engine of this design built by Mr. Eeynolds for the 
World's Fair at Chicago, an auxiliary eccentric operated levers on the 
governor in such a manner as to cause the knock-off block to follow the 
hook until cut-off occurred, but in all details the valve motion is appar- 
ently the same as on other engines. To come to a full' understanding of 
the peculiar features in the design and operation, a careful study of 
the complete movement during a revolution of the crank is necessary. 

Fig. 177 is a view of the valve-gear side of this type of engine. The 
eccentrics are in the case A, the steam eccentric rod is indicated by B, 
and the exhaust by C, while the steam and exhaust rods are respectively 
at D and E. It will be noted that the motions from the eccentrics to the 
wrist plates are direct. The steam and exhaust wrist plates, valve rods, 
etc., can be easily traced from Fig. 177. 

To obtain the first impression of how the interior of the valves look, 
refer to Fig. 178, in which the steam and exhaust valves on one end of 
the cylinder are shown with the valve gear removed and the valves and 
ports in cross section, while on the other end the valve cranks have been 
left in place and show their relative position to the valves at the opposite 
end. The steam and exhaust wrist plates are shown at A and B, respec- 
tively, and above A is sho-wni the travel circle C of the steam eccentric; 
below is the exhaust circle D. In these circles the crank position is at 
c, and e is the eccentric position. The steam-valve crank is indicated by 

172 



174 



VALVE SETTING 



E, the exhaust- valve crank hjF; G is, the bell crank and H the knock-off 
cam. On the other end of the cylinder where the valves and ports are 
in cross section, the dotted lines E', F', G' and H' denote the center lines 
of the same parts on that end, and the arcs at the ends of these lines 
show the respective positions of the pin centers. From each end of these 




FIG. 178. 



arcs the center lines show the positions of the pins when they reach their 
respective extremes of travel. 



Steam Valves Open at Both Ends When Hooked Up 

In Fig. 178 the wrist plates and all connected parts are shown in 
their central positions, at which the exhaust valves are lapped, as is 
usual in practice, but the steam valves are open on both ends when they 
are hooked up. If hooked up and not released the steam valves would 
be open from the beginning of one stroke up to 75 per cent, of the return 
stroke, but when the knock-off cam-pin center is at a, the cut-off will 
be carried out to about seven eighths or eleven twelfths of the stroke, and 
the cut-off will occur just before the steam valve on the opposite end picks 
up for lead. When the knock-off cams are in the. position represented by 
the lines H and H', Fig. 178, the cut-off will occur at about three eighths 



THE REYNOLDS LONG-RANGE CUT-OFF 



175 



of the stroke, and when the knock-off pin center is at h the valves will 
remain lapped, being dropped before they can open. If the regulator is 
allowed to drop down so the knock-off cam pin will reach the point c, 
the valves will not pick up and will remain lapped. This peculiarity 



must be thoroughly fixed in mind. 



When an ordinary valve is at the center of its travel, it is lapped on 
the steam edges and full open to the port when at the extreme of its 
travel in one direction; at the other extreme of travel it is closed. With 
the engine under discussion the steam valves are lapped at the extreme 




FIG. 179. 

throw of the eccentric in one direction, and full open at the other extreme, 
having minus lap when at the center of travel. 

When the steam valve is lapped th.e proper amount, the dashpot 
plunger is down at the bottom of its travel, and the cranks E and E' are 
at the lowest positions of their travels. The eccentric must come over 
to its extreme position in order that the valve may be picked up. Owing 
to the dashpot and method of cut-off on a Corliss engine, this arrange- 
ment can be applied, but is not applicable to any other type of valve. 

For the purpose of illustration let it be assumed that the steam valves 
pick up and do not cut off through the medium of the knock-off cam, and 
let us follow the action of one valve throusrh one revolution of the 



176 



VALVE SETTING 



crank. In Fig. 179, the valve cranks are in their extreme positions, and 
the eccentrics likewise, with everything ready to start in the direction of 
the arrows. On the crank end the steam valve is lapped and the exhaust 
valve is open, while reverse conditions exist on the head end. On all other 
types of valve gear the eccentrics would he advanced 90 degrees when the 
valves are lapped, hut on this engine the steam valve is lapped when 
the eccentric is on its extreme position. The exhaust valves are the 
same as on any other double-eccentric Corliss engine. 

In order to get the positions of the eccentrics in relation to the 
crank, we will advance the steam eccentric until the proper amount of 




FIG. 180. 

lead is obtained, and the exhaust eccentric until the proper amount of 
closure is reached. From Fig. 180 it will be seen that the steam eccentric 
is only some 30 degrees in advance of the crank, or only enough to 
overcome the lap and lead, and the exhaust eccentric follows the crank. 
Assuming that the eccentrics have been made fast to the shaft in these 
relative positions, we will now move the crank around in the direction of 
the arrows until the position shown in Fig. 178 is reached, where it will 
be noted that the crank has advanced on the first half of its revolution 
some 60 degrees or thereabout. 

In Fig. 181 the eccentrics are shown in their extreme positions oppo- 
site to that at which they started and the steam valve is shown wide open 



THE REYNOLDS LONG-RANGE CUT-OFF 



177 



with the exhaust valve closed as far as it will go. The next positions 
indicated in Fig, 182 show the steam valve closed when the crank has 
reached approximately 75 per cent, of its return stroke. This would, of 
course, prevent the practical operation of the engine unless the regulator, 
through the knock-off cam, does its work of cutting off at the proper 
moment. 

It is well to bear in mind that when the steam valve carries out to 
the latest point of cut-off, it is released before the other steam valve picks 
up to open, and that while the release of the steam valve varies, the 
pick-up does not. It is thus impossible for both steam valves to be open 




^'f- 



FIG. 181. 

at the same time, although they may appear to be arranged to the con- 
trary. On an ordinary Corliss engine the valves will hook up without 
releasing when the regulator is at its lowest working position, but with 
this type the valves are released alternately every stroke, no matter how 
low the regulator, unless it is in the safety position, when the valves 
would not pick up at all. 



Setting the Valves 

Bearing these points in mind we may proceed to set the valves. The 
amounts of lap and lead and the positions of the cranks from the center 



178 



VALVE SETTING 



lines given herewith are for engine cylinders of 36-, 42-, 48-, and 60- 
in. stroke. 

First set the wrist plates central and clamp them in place; then adjust 
the lengths of the rods so that the steam valves are open 11. in., 
as shown in Fig. 178, and the exhaust valves are lapped ^ in. If 
the rod lengths are right the center lines of the cranks E and E' will 
coincide, the pins of the cranks F and F' will be ^ in. from the 
center line, as shown, and the pins on each end of the bell cranks G and 
G' will be 23- ins. and A- in. from the center lines. When the valves 

° lb 




FIG. 182. 



have been set with the wrist plates central, release the wrist plates and 
roll the eccentrics around the shaft to test them and the reach rods, and 
see that they are of the right length to make the wrist plate travel equally 
each side of the center line. 

Then place the crank on center and pull the steam eccentric around 
enough to give J^o-in. lead, and make it fast. Next move the engine 
around in its direction of travel to about 95 degrees of its stroke and 
move the exhaust eccentric around until the exhaust valve on the same 
end is just opening or releasing. Make the exhaust eccentric fast and 
move the engine around its full revolution and check off the valves on 



THE REYNOLDS LONG-RANGE CUT-OFF 179 

the other end and the exhaust closure. Then set the regulator up to its 
central position and adjust the lengths of the rods from the lever to the 
knock-off cams, so that the pins of the cams H and H' will set % in. off 
the center line, as in Fig. 178. Let the regulator down and hook up the 
wrist plates; then pull the engine around to make sure that the steam 
valves are released on each stroke alternately at not later than eleven 
twelfths of the stroke, and always before the other valve picks up. 



XIX 

THE DUPLEX PUMP* 

As is well known, the slide valves of a duplex pump have neither out- 
side nor inside lap. This is necessary to prevent the pump from stopping 
should the valves be in a position to cover all ports. By making the length 
of the valve the exact distance from the outside edge to the outside edge 
of the steam port, and the exhaust cavity the exact distance from the inside 
edge to the inside edge of the exhaust port, there is only one point in the 
travel of the valve where ports are completely closed; and it is not likely, 
if it ever should happen that both valves were in this position, that the 
pump would fail to start off, for the leakage of steam past the edges of 
the valves will never be exactly the same in all four corners, therefore the 
equilibrium would be destroyed quickly. 

By setting the outside edges of the valves "line on line'^ with the out- 
side edges of the steam ports, the valves will stand in a central position. 
If, then, both rocker arms are put in a central or vertical position, the clear- 
ance on the valve rod must be the same on both ends. In Fig. 183 this 
clearance is shown inside of the steam chest and is marked C. On larger 
pumps usually, a lost-motion link is inserted between the crank and the 
valve-rod clevis, which can be adjusted without taking off the steam-chest 
cover. No fixed rule can be given for the amount of this clearance, as it 
must be adjusted to suit the working of the pump. 

On a pump of ordinary proportion, such as a boiler feed pump, the total 
clearance, 2 C, should equal about 25 per cent, of the travel T of the crank 
pin at nominal stroke. On a low-service pump (also on a pressure pump 
for moderate pressure) it is often found that the reciprocating parts are 
so heavy that the cushion, with the cushion valve shut tight, is not 
sufficient to stop the motion of the piston at the end of the stroke. In 
this case the lost motion should all be taken up. If the piston does not 
make a full stroke, the lost motion may be increased somewhat above 
the figure given, but it must be kept in mind that this will reduce the 
travel of the valve and the port opening, and thus may affect the speed 
of the pump. 

* Contributed to Power by F. F. Nickel. 
180 



T1I2 DUPLEX PUMP 



181 



The Cross-exhaust Valve 

In the case of ca compound pump there is still another appliance that 
can be brought into action to regulate the length of the stroke, and that 




FIG. 183. 



is a connection, provided with a valve, between the two high-pressure ex- 
haust pipes. The object of this connection is to equalize the pressure in 



182 



VALVE SETTING 



these exhaust pipes and make it more uniform. This is called the cross 
exhaust, and its influence on the distribution of steam is clearly , shown by 
Figs. 185 to 190 inclusive. Figs. 185 to 188, inclusive, are convenient sec- 




FIG. 184. 



tional plans of the steam cylinders of a compound pump, with the pistons 
in positions that correspond to lines A — B and B — C in the diagram Fig. 



THE DUPLEX PUMP 183 

190. Fig. 189 represents a diagram with the cross exhaust closed. The 
steam pressure follows up the full stroke in the high-pressure cylinder, and 
when the exhaust valve opens it blows into the intermediate space and 
mixes with the steam left therein from the preceding stroke. 

Assuming the intermediate space to have a volume equal to 0.75 of that 
of the high-pressure cylinder and a cylinder ratio of 1 to 3, we have the 
following volumes : 

High-pressure cylinder = 1 ; intermediate space = 0.75; low-pressuro 
cylinder = 3. 

Clearances are neglected, as it is only intended to show the action of 
the cross exhaust. We will also assume that the steam expands according 
to Mariotte's law : 

p X. V = constant, 

which is sufficiently accurate for our purpose, and assists greatly in getting 
a clear conception of the behavior of the steam as it passes through the 
various stages. 

The amount of steam passing through one side of the engine is evidently 
one high-pressure cylinder full at initial pressure. Its measure is p X ^ = 
120 X 1 = 120 lbs. When the high-pressure exhaust valve opens, this 
steam flows into the intermediate space, where it meets and mixes with 
steam that was left there from the preceding stroke. This steam was shut 
off from its communication with the steam in the low-pressure cylinder 
when its exhaust valve opened and must be at the same pressure as the steam 
in the low-pressure cylinder at the point of exhaust. As the ratio of cyl- 
inders was assumed to be as 1 to 3, the steam expands three times as it 
passes from the high-pressure cylinder to the low-pressure cylinder, and the 
terminal pressure is therefore 

120 

= 40 lbs. 



It will be noted that 120 is a measure for the steam passing through the 
engine and this amount is accounted for by the indicator diagram at every 
point of the stroke. Thus we have : 

High-pressure cylinder, p X ^ = 130 X 1 = 120. 

Low-pressure cylinder, ^X^ = 40X3 = 120. 

The amount of steam that is constant and remains in the intermediate 
space is 0.75 X 40 = 30 lbs. ; the two combined give 120 -f 30 = 150 lbs., 
which when distributed over a volume ofl-}-0.75=rl.75 results in a pres- 
sure of 

150 

— 85 lbs. 

1.75 



184 



VALVE SETTING 



This means that when the high-pressure exhaust valve opens the steam 
expands from the high-pressure cylinder into the intermediate space from 
120 to 85 lbs. without doing any useful work. From 85 lbs. it then ex- 



120 Lb. 



.3 
Vol. 



B 



.75 Volume 



2.1 

Volumes 



40 Lb. 



Left Hand Side 



.75 Volume 











c 


S Steam Valve 
f about to open. 


M, Exbaust Valve 
^ about to open. 




m 




1 Volume 
120 Lb. 




>■ 


=:: 








A 


40 Lb. 











Bight Band Side 



FIG. 185. 



Vol. 



S6.5 
Lb. 



2.1 

Volumes 



56.S Lb. 



Left Hand Side 



S6.5 Lb. 



.75 Volun 


le 






56.5 Lb. 




1 












1 




, 


m 




I Volume 
56.S Lb. 




< — 










A 


6 Lb. 






1. 






i 







Bight Hand Side 



FIG. 186. 

pands from the high-pressure cylinder through the intermediate space into 
the low-pressure cylinder doing useful work upon the low-pressure piston. 

With two points of the expansion curve, namely, 85 lbs. at the begin- 
ning and 40 lbs. at the end of the stroke, it is now easy to construct the 
remainder of the curve, as it is only necessary to complete the rectangle 



THE DUPLEX PUMP 



185 



and draw the diagonal. Where this diagonal meets the line of zero pres- 
sure, there is point o, the zero point of pressure and volume. Any line 
drawn through this point o will give the volume on the line 85, Fig. 189, 
and its corresponding pressure on line A, Fig. 190. 



^ C 



3 Volumes — 



I .75 Volume" 



.3 
Vol. 



B 



2-1 

Volumes 



FIG. 187. 



1 Volume 
56.5 Lb. . 



.75 Volume 



3 



.75 Volume 



.3 
Vol. 



56.5 
Lb. 



120 Lb. 



B 



2.1 
Volumes 



FIG. 188. 



Under the conditions indicated in Fig. 189, it cannot be expected that 
an ordinary pump will work satisfactorily, as the following comparison of 
the steam forces will show: 



186 VALVE SETTING 

Beginning of stroke: 

H. P., 120 - 85 = 35 

L. P., 85 - 6 r= 79 X 3 = 237 



End of stroke 



Total steam force 272 lbs. 

H. P., 120 - 40 =r 80 

L. P., 40 - 6 = 34 X 3 = 102 

Total steam force 182 lbs. 



The average of the two, or 

272 + 182 



227 lbs., 



is a measure of the resistance which, in a pump, is constant throughout the 
stroke. There is, therefore, at the beginning of the stroke, a surplus of 




FIG. 189. —CROSS EXHAUST CLOSED. 



272 — 227 = 45 lbs., and at the end a deficiency of 227 — 182 = 45 lbs. 
If, however, the cross exhaust is opened, it equalizes these two forces to a 
certain extent and modifies the diagram, as shown in Fig. 190. 

With the assistance of Figs. 185 to 188, inclusive, it is easy to follow 
the steam through its various stages. In Fig. 185 the pistons of the right- 
hand side have completed the stroke and are about to return. The cylinders 
on the other side and intermediate spaces are filled with steam at the low- 
pressure terminal, or 40 lbs. The total amount of steam is then 



120 X 1 == 
40 X3.9 = 

Total 



120 
156 

276 



THE DUPLEX PUMP 
which divided by the volume, 4.9, gives a resulting pressure of 

276 



187 



4.9 



= 56.5 lbs. 



as shown in Fig. 186. This increased pressure gives the low-pressure piston 
of the left-hand side an additional push and enables it to complete its 
stroke while the steam expands down to 40 lbs. again. Then the steam 




56.5 



FIG. 190. — CROSS EXHAUST OPEN. 



fiom the left-hand high-pressure cylinder flows into the intermediate space 
and raises the pressure to 56.5 lbs. in order to help out the right-hand low- 
pressure piston. 

Fig. 190 shows this action clearly, but in practice the rise in pressure 
will not be as abrupt as shown there, as the pulsations in the pipes will still 
more equalize the differences and produce a practically uniform pressure 
in the intermediate space. 

It will also be noted that by opening the cross exhaust, pressure is re- 
moved from the low-pressure piston and shifted over to the high-pressure 
piston, which results in a loss of power and reduced speed of the pump. 

The cross exhaust should therefore be kept closed whenever the pump 
runs fairly well in this condition. 



XX 

AIE COMPRESSOES* 

In an air compressor, as well as in a steam engine, clearance between 
the piston and cylinder heads has to be allowed, for mechanical reasons, 
when the piston reaches the end of its stroke. This clearance space is 
augmented by the cubical contents of the suction and discharge ports, the 
pockets for piston-rod nuts, etc. The clearance volume should be made 
as small as possible for the following reasons : 

(a) To diminish the friction loss due to compressing and reexpanding 
of the air confined in the clearance space at the end of the stroke. 

(6) To attain as high volumetric efficiency as possible. 

(c) To avoid the slow opening of suction valves, which increases the 
suction loss. 

Using the same lettering to distinguish the various sections, an ex- 
planation of these points may be made as follows: 

(a') The energy contained in the air confined in the clearance space 
ought not to be lost; this air should be reexpanded on the return move- 
ment of the piston, thus giving back most of the work required for its 
compression. Part of this work, however, will be lost in the friction of 
the air compressor and, on account of the work unavoidably expended in 
friction during the compression and reexpansion of the air, it is desirable 
to make the clearance volume as small as possible. 

{¥) The suction air valve must not be opened before the compressed 
air in the clearance space has been reexpanded; if it is opened before the 
pressure has been reduced by such expansion to that of the air supply, com- 
pressed air will rush out through the suction ports and the energy stored 
up in this air be lost. The larger the clearance the later the suction valve 
should be opened for the admission of fresh air; consequently, the smaller 
will be the quantity of fresh air taken in, and the capacity of the com- 
pressor is correspondingly reduced. The volumetric efficiency of a compres- 
sor is the ratio of the volume of air in cubic feet taken in through the 
suction valves to the displacement of the piston in cubic feet, provided 
the valves are tight. 

To show the influence of an increase in clearance on the volumetric 

* Contributed to Power by Claude Aikens. 

188 



AIR COMPRESSORS 189 

efficiency of an air compressor, let us assume a 22 X 3(3-in. air compressor 
taking air in at atmospheric pressure, discharging it at 30 Ihs. gauge and 
having 1^ per cent, clearance, as compared with one having 5 per cent, 
clearance. 

The cylinder volume being proportioiuil to the stroke, the clearance 
volume may be expressed in inches of stroke; thus, 1^ per cent, clearance 
equals 0.015 X 36 := O.o-t in. of stroke. The air confined in the clearance 
space expands very nearly adiabatically; that is, not losing any heat to 
its surrounding walls or receiving any from them, especially if the heads 
of the air cylinder are not cooled. The formula for adiabatic expansion 
of air is : 

P V 1.41 = Constant, 
where 

P = pressure per square inch, 
and 

V = volume in cubic feet. 

The part of the stroke required for the reexpansion of air from 44.7 
to 14.7 lbs. absolute is 



(jj^) 7^-1 1X0.54 = 0.648. 



•V i-ti A 



The volumetric efficiency, as far as clearance is concerned, is therefore 
36-0.648 



36 



= 0.982 



or the capacity of the air compressor is 100 — 98.2 = 1.8 per cent, less 

than the piston displacement. 

As the percentage of decrease in capacity is directly proportional to the 

percentage of clearance, with 5 per cent, clearance the capacity will be 

decreased 

5 X 1.8 ^ 

— — — = 6 per cent. 

J..D 

(c') Another and very important reason for desiring small clearances 
in air compressors having positively operated suction valves is that the 
opening of the suction valve becomes the slower in relation to the speed 
of the piston the later it opens, or, in other words, the larger the clearance. 

If the suction valve begins to open when the piston moves at a com- 
paratively high speed, the air has to assume a high velocity in order to 
follow the piston. As a consequence, the pressure in the air cylinder 
will be considerably lower than that of the outside air and the work the 
compressor has to do is uselessly increased. 



190 VALVE SETTING 



Determining Relative Positions of Crank Pin and Eccentric 

The relative positions of the crank pin and eccentric may be determined 
graphically or by calculation. 

Assuming the same conditions as stated, the part of the stroke required 
for reexpansion from 44.7 lbs. absolute to 14.7 lbs. absolute is 0.648 in. 
Graphically, proceed as follows: In Pigs. 191 and 193 draw the crank-pin 
circle, B = 18 ins., and find the ends of stroke of compressor, 2R = 36 ins., 
by laying off the length of the connecting rod, L = 108 ins., from the 
extreme crank-pin positions; then measure the points X =: 0.648 in, from 
each end of the stroke, giving the piston positions at which the suction 
valve should open. With i as a radius and the points X from the ends 
of the stroke as centers, determine the points of intersection with the 
crank-pin circle. This gives the positions of the crank pin at which the 
inlet valve should open. ' 

By calculation the crank angle corresponding to a piston movement of 
0.648 in. is: 

For head end (see Fig. 191), 

R2j^B--U- X {2L - X) 

Cos. y= ^7715 = 1 



2R B ZH {L- X-\-R) 

0.648 (216 - 0.648) 



= 0.96908 



= 1-36 (108 - 0.648 -f 18) 

= 14 degrees 17 minutes. 

For crank end (see Fig. 192), 

L^-R^--B^ X{2L-\-X) 

Cos. y = rPTB = 1 



2RB 2R{L-R-\-X) 

0.648 (216-1-0.648) 
= 1- 36 (108- 18 + 0.648) =»-^^''^^ 

= 16 degrees 52 minutes. 

The suction valve on the crank end should, therefore, open when the 
crank has moved 16 degrees 52 minutes past the dead center and, of course, 
it should close just when the crank reaches the inner dead center, so that 
the suction valve opens and closes while the crank travels through an 
angle of 

180 degrees — 16 degrees 52 minutes. 

The eccentric moves through the same angle as the crank, and its 
■opening motion must be equal to its closing motion; it has, therefore, an 
equal amount of motion on each side of the horizontal center line during 



AIR COMPRESSORS 191 

the suction period of the compressor. The position of the eccentric, when 
opening the suction valve, must be 

180 degrees — 16 degrees 52 minutes 

■ = 81 degrees 34 minutes 

from the inner dead center, the valve gear being designed M^ith the eccentric 
leading the crank. 

Due to the angularit}^ of the connecting rod, the position of the eccen- 
tric for the forward and return stroke would not be the same. A com- 
promise may be made, but it is sufficient to decrease the lap of the suction 
valve at the head end, so that the valve opens at the proper time. It will 
close, then, a trifle after the crank has passed the dead center, in this case 
about 2 degrees 35 minutes late (see Fig. 193). The reason for this may 
be seen from the fact that the inlet valve at the head end opens after the 
crank has passed 14 degrees 17 minutes beyond the dead center; the center 
of the eccentric will be 

81 degrees 34 minutes -\- 14 degrees 17 minutes = 95 degrees 51 minutes 

from its dead center at the head end, or 5 degrees 51 minutes beyond its 
mid travel. The inlet valve remains open until the eccentric reaches the 
corresponding position on its return stroke. Opening and closing must, 
therefore, take place while the eccentric travels through 

180 degrees — (2X5 degrees 51 minutes) = 168 degrees 18 minutes. 

The crank moves through the same angle and the piston from the dead 
center at the head end is 

14 degrees 17 minutes -\- 168 degrees 18 minutes = 182 degrees 35 minutes. 

The piston is, therefore, on its return stroke and has traveled a distance 
equal to the radius of the crank times 

1 — Cos. 2 degrees 35 minutes = R {1 — 0.999) = 0.018 in., 

an insignificant amount. 

Referring to the valve gear itself, the working edges of the valves and 
ports are shown by radial lines A, B, and C, Fig. 194, on the ends of the 
valves and valve chests, at the side of the cylinder opposite the wrist plate; 
for each port there is a mark on the cylinder coincident with the edge of the 
port which is toward the end of the cylinder barrel; and for each valve 
a mark on the back end of the valve coinciding with the edge of the valve 
which is toward the end of the cylinder barrel. 

Fig. 195 shows the wrist-plate central for adjusting the valve connec- 
tions. A central mark on the back hub of the wrist plate and three marks 



192 



VALVE SETTING 




png ^BJo 



pna pTOH 



AIR COMPRESSORS 



193 




pngp^H 



194 



VALVE SETTING 



on the wrist-plate stand, which is bolted to the cylinder, show how the 
eccentric motion is to be adjusted so that the wrist plate will travel cor- 
rectly when in motion. The two outer marks indicate the extremes of 
travel, and the central mark of the wrist plate, when in line with the 
single mark on the hub, shows that the wrist plate is central. 

To Set the Suction Valve 

To set the suction valve as shown in Fig. 195, first place the mark on 
the wrist-plate hub even with the central mark on the wrist-plate stand; 
then adjust the valve connections to give the suction valves the lap shown 




FIG. 194. 



on the drawing. The wrist plate should now be connected to the eccentric 
by the rods and, being in its central position, the rods must be adjusted 
so that the eccentric also is in its center of motion. The eccentric can now 
be secured to the crank shaft after the crank pin is moved relatively to 
the center of eccentric until the angle included between their respective 
centers is as determined by the calculation given; in the example, 81 de- 
grees 34 minutes, the eccentric leading the crank in the direction of motion. 
After the valves have been set as accurately as possible when cold, and 
the movement of the forward and back strokes equalized, as explained, 
indicator diagrams should be taken and the eccentric rod adjusted to cor- 
rect any slight irregularities. 



AIR COMPRESSORS 



195 




196 



VALVE SETTING 



For single-stage air compressors and in the high-pressure cylinders of 
two-stage air compressors the Allis-Chalmers Company, of Milwaukee, uses 
as a standard the arrangement of valves shown in Fig. 196. Eotary valves 
are used for the inlet and plain single-beat poppet valves for the discharge. 
The inlet valves are driven by an eccentric on the main shaft, and, by 
means of the wrist plate, they are given the quick opening and closing, 
and the slow movement when the ports are covered and the valves under 
pressure, which is characteristic of the Corliss valve gear. The inlet 
ports are of ample size, short and direct, and the air is guided into the 
cylinder by an easy curve, thus reducing the entering friction and insur- 



ji«M|«|^g-M'% 


^^^^M 


W^^': -^ ■ Ml r -■-' 




^^^^^HH l_._ 




.. --x! 


I- 


^^9Piii^^»^HM^^H 


jl«i-" "■ 


_ ^^||||HM|||l|^H|H^HH 


I^Sj 


'^^K:^^n 




i^'^H^^nHm 


lk 


l^m 




iH^^ 








phh 


J 



FIG. 196. — AIR CYLINDER WITH AUTOMATIC DISCHARGE. 

ing the complete filling of the cylinder with as little loss in pressure and 
at as nearly the outside pressure as possible. 

The discharge valves are of the drawn-steel cup type and open auto- 
matically when the pressure in the cylinder equals the discharge pressure. 

A modification of the valve gear shown by Fig. 196 is illustrated in 
Fig. 197. In this gear the inlet valves are operated the same as in Fig. 
196, but the discharge valves are mechanically closed, being free to open 
automatically, and positively closed by plungers operated by connections 
to a wrist plate driven by an eccentric on the main shaft. The movement 
of the plungers of the discharge valves is so timed as to positively bring 
the valves to their seats just as the piston reaches the end of its stroke, 
thus avoiding any slip of air back by the valves and also to avoid slamming 
when the piston commences to return. This design is also indicated by 
Fig. 199, showing the valve gear of a blowing engine. As soon as the 
valves are closed the plungers recede, leaving the valves held to their seats 
by the discharge air pressure until that point in the return stroke of the 







'"xi ^ffl?^& M- 


il9 im 
'1— 






V Bm nHwti il .^£iH J 


IMfT 


\ ^^^Smmm^JV ^ -^HI "' ^^^^1 1 ^1 


£ 


m^r^y-i-iifll 


,^-^ - 


^^H 


1 -^^ 


; 1 


r 

< 




^^B t 


^^^ 


Li 


M 




^^^^B '' "^B *" ^^w^™«» i 


^ 1 






" ,i, ■ ****!:— C~ - 


« 


I 






ftfr^ 




1 ^^ ' mmt 


d 


-i-^^M^^- 


i; 


■■'Ml. 




M~~ "[I^ 


^^^IB^-^V 


mTvSF 


' ii 


^^^^i 


^V 



198 



VALVE SETTING 



piston is reached where the pressure in the cylinder equals the discharge 
pressure, when the valves are free to open automatically. In closing, the 
air between the plunger and valve forms a cushion which is so adjusted 
and gradually reduced that the valve is brought gently to its seat without 
noise or pounding. 

A third type of valve gear is shown in Fig. 198. In this both the inlet 
and discharge valves are of the rotary pattern, positively operated by inde- 
pendent eccentrics on the main shaft. The inlet valves are the same as 
decribed in the two preceding t5'pes. The discharge valves are so propor- 
tioned and adjusted as to close positively just as the piston reaches the 




FIG. 198. — AIR CYLINDER WITH MECHANICAL DISCHARGE VALVE. 

end of its stroke and to open at any predetermined maximum discharge 
pressure required. In addition to the rotary discharge valves, the cylinder 
is fitted with auxiliary poppet valves of the steel-cup type, which serve 
as relief valves in case the eccentric should slip; or for allowing the air 
to be discharged from the cylinder, should the pressure, for any cause, 
fall below that at which the main discharge valves are set to open. 



How TO Set Blowing-engine Valves 

Having considered the procedure necessary for setting the air valves of 
compressors, together with some of the factors involved in their design, 
it will be of interest, in conclusion, to note the directions to be followed 
in the case of a blowing engine, which, although very simple, is sometimes 
puzzling to operating engineers lacking exact information on the subject. 

Referring to Fig. 199, when the engine crank' pin is on either the top 



AIR COMPRESSORS 



199 



or bottom dead center, set the wrist plate exactly central; that is, when 
the piston is at the top or bottom of the stroke, the pins M M' should lie 



in a straight line between P C and P C. 



For setting the inlet valves first put the piston at the top of its stroke, 
the wrist plate being central, adjust the connections B and B' until the 



Horz. Line 




FIG. 199. 



inlet pins B D' are inches from the horizontal line, and adjust the 

valve stems G G until each of the top inlet valves are lapped inches. 

Next turn the engine over, set the piston at the bottom of the stroke, the 
wrist plate again being central, adjust the valve stems H H until each of 



AIR COMPRESSORS 201 

the bottom inlet valves is lapped inches; then lock the valve stems 

securely. 

For setting the discharge valves, put the piston at the bottom of the 
stroke, the wrist plate being central, adjust the connections A and A' until 

C and C" are each inches from the horizontal line, and then adjust 

the valve stems E E and F F until each of the valves touches its seat ; 
then turn off a quarter turn and lock them. Then turn the engine over 
and set the piston at top of the stroke and see that the valves are in the 
same position as when the piston was at the bottom. 

The amount of lap, etc., indicated by the spaces in these directions 
varies, of course, with each machine, and the figures can either be obtained 
from the builders, or may be worked out in accordance with the method 
described earlier in this chapter. 

In the various gears described the valves are placed in the cylinder 
heads, thus reducing the clearance to the minimum ; all of these valves are 
readily accessible and can be removed and replaced without difficulty and 
without disturbing the adjustment. It may be said, also, that while the 
foregoing mentions only compressors and blowers for handling air, it applies 
as well to machines designed for other gases, as far as the general principles 
involved are concerned. Special apparatus, however, requires special treat- 
ment and the builders should in all cases be required to furnish specific 
directions for setting the valve gear supplied with their machines. With- 
out this, misunderstandings occur which sometimes cause serious trouble. 



INDEX 



Admission, angle 12 

effect of angularity of con- 
necting rod 15 

of changing valve 

setting 20 

of steam 39, 40 

openings, maximum 101 

period 13 

point of . . . .33, 34, 35, 36, 124 

finding 21 

Advance, angle 34, 36, 116 

angle, finding. .21, 22, 23, 24, 26 

maximum 45 

angular, effect of changing. . 

127, 128 
of eccentric, angular, chang- 
ing 19 

Ahead of crank, defined 43 

Aikens, Claude 188 

Air compressors 188 

compressor, volumetric efficiency . 1 88 
with automatic dis- 
charge. . 196 

cylinder with mechanical dis- 
charge valve 197, 198 

Allis-Chalmers Co 172, 196 

Angle behind crank, cut-off valve. . . 44, 45 
crank, corresponding to piston 

movement 190 

of admission 12 

of advance 34, 36, 116 

finding. 21, 22, 23, 24, 26 

maximum 45 

of rod, correcting for 18 

finding 16 

Angular advance, effect of changing. . 

127, 128 

finding 12 

of eccentric. .11, 84, 99 
of eccentric, chang- 
ing 19, 20 



PAGE 

Angularity of connecting rod 15, 191 

of rod, correcting for 17 

Balanced piston valve 135 

steam valve 115 

valves 93, 96, 103, 108, 113 

Behind crank, defined 44 

Blowing-engine valves, setting 198 

Brown engine 76 

governor 78 

setting valves 79 

Buckeye engine 92 

piston valve 100 

Cam, trip 68 

Catch block, clearance 59 

Center, dead 35, 39, 51 

finding 46,122 

line 49, 50 

putting engine on. 138 

Central marks on hub of wrist plate . . 59 
Centralization of valve gear, double 

eccentric engine 61 

Circle, crank 36 

of reference 36 

valve 30 

Clearance, amount 88 

at catch block 59 

at ends of steam cylinder, 

equalizing 53, 54 

obtaining 80 

of cylinder 53, 54 

on valve rod 180 

space 188 

Compoimd engine 125 

Sturtevant 135 

Compression 126 

amount 82, 148 

effect of changing valve 

setting 20 

point of 34, 35. 36 



203 



204 



INDEX 



Compression, point of, finding 23 

Condensing engine, lead of low-pres- 
sure valve 125 

Connecting rod, angle, finding 16 

angularity 15, 191 

Conliss engines, tables showing prin- 
cipal dimensions and horse 
power with different steam 
pressures and points of cut- 
off 56, 57 

steam engines 53 

Correcting for angle of rod 17, 18 

Crank angle corresponding to piston 

movement ; 190 

when compression be- 
gins, finding 27 

circle 36 

on dead center 47 

pin and eccentric, determining 

relative positions 190 

position 115 

position. 6, 7, 8, 9, 30, 32, 33, 39, 40 

travel 41 

Cross-compound engine, setting ec- 
centric 127 

Cross-exhaust closed 186 

open. 187 

valve 181 

Cut-off 40, 168, 174 

adjusting 127 

changing 82 

early 43, 45, 46, 127, 167 

Greene . 62 

late 45, 127, 167 

later than one-half stroke 45 

point of.. 4, 15, 18, 34, 35, 36, 

40, 41, 42, 43, 44, 99, 124 

point of, finding 23, 24 

Reynolds long-range 172 

rods, adjusting. Rice & Sar- 
gent engine 1 50 

valve 95, 97 

Meyer 38, 39 

operation 38 

position 99 

Cylinder pressure 96 

valves, details 107 

D slide valve 19 

Dashpot rod, length 58, 59, 154 

stem, adjusting 80 



PAGE 

Dead center 35, 39, 51 

finding 46, 122 

Details and measurements, Sturte- 

vant compound engines. .. . 144 

of link 107 

Diagram, indicator 35, 119 

making 9 

necessary data for con- 
structing 36 

of high-speed engine 35 

of side shaft 131 

taking 142 

using . 19 

valve, use 21, 30 

Zeuner slide-valve 23, 29 

Dimensions with different steam pres- 
sures and points of cut-off, Corliss 

engines 56, 57 

Double eccentric engine, valve setting, 

60, 61 

Double-ported main valve 97 

valves 156 

Dow, Carl S 135 

Drainage systems 142 

Duplex pump 180 

Eccentric 40 

adjustable 135 

low-pressure 139 

and crank pin, determining 

relative positions 190 

angular advance 11, 84, 99 

changing .19, 20 
cross-compound engine, set- 
ting 127 

linear advance 11 

low-pressure, adjusting 137 

motion, adjusting 194 

on dead center 47, 48 

point of minimum cut-off.. . 126 
position. .3, 6, 7, 8, 9, 32, 39, 
40, 41, 45, 46, 51, 

115, 176 

changing 43 

rod, length ..42, 73, 75, 170, 171 

too long 72 

setting 101, 102 

travel 41, 46, 70, 165 

Eccentricity, changing 20 

Engine, Brown 76 

Buckeye 92 



INDEX 



205 



PAfJE 

Engine, changing speed 150 

compound 125 

Fitchburg Ill 

Fleming piston-valve 121 

Greene-Wheelock 62 

heavy duty 1 56 

Mcintosh & Seymour 84 

Porter- Allen 103 

Putnam 130 

putting on center 138 

"Rehance" 156 

Rice & Sargent 145 

setting at half stroke 51 

steam, Corliss 53 

Sturtevant compound 135 

Wright 159 

Equality of maximum admission 

openings 101 

Equalizing pressure in exhaust pipes. . 181 

Exhaust 15 

clearance 11 

effect of changing valve set- 
ting 20 

gear 147 

lap 32, 36 

definition 10 

effect of changing 128 

positive and negative 10 

lead 33, 34, 36 

motion 115 

point of 17 

valve 68, 113 

valves, adjusting 75 

equalizing movement 81 

rod, length 60 

setting 81, 148 

stem, length 81 

Expansion, effect of changing valve 

setting 20 

Fitchburg engine Ill 

Flat-balanced valves 108 

Flat-side valves 103 

Flat valve 93, 96, 108 

Fleming piston-valve engines 121 

Gauge for adjusting clearance 54 

Gear, details 86 

valve 103, 111 

Governor, adjusting 82, 143 

Brown engine 78 



Governor, case, location 117 

in position 139 

inertia 138, 139 

Porter fly-ball 106 

jwsition 99 

Rites inertia, Rice & Sar- 
gent engines 149 

rod, adjusting 60 

shaft 119 

Greene cut-off 62 

Greene-Wheelock engine 62 

setting 

valves.. 73 

valve gear. 64 

Gridiron valve 62, 84, 88, 159, 161 

Hall, Thomas 121 

Hawkins, E. S 19, 29 

Heavy duty engines 156 

High-pressure side of Greene-Wheel- 
ock cross-compound 

engine 63 

valve 140 

setting 138 

Hill valve 62 

Horizontal engine, valve gear 84 

travel of pin 97 

Horse power with different steam 
pressures and points of cut-off, Cor- 
liss engines 56, 57 

Indicator diagram 35, 194 

making 9 

rig 141 

use 30, 82, 118, 134, 142 

Inertia governor 138, 139 

Inlet valve 65, 67 

gear, operation 146 

Inside lap 32 

Johnson, F. L 130 

Keying up pin bearings 120 

Lap 32, 50, 163, 165, 175 

adjusting 79, 89, 157 

valves for 75 

amount 59, 154, 177, 194, 201 

changing 19, 20 

definition 4 

effect 4 



206 



INDEX 



Lap, exhaust 10, 32, 36 

definition 10 

effect of changing. . . . 127, 128 

finding 21, 23, 24, 25, 26, 27 

inside 32 

necessity for 31 

negative, definition 11 

outside 32 

steam 31, 32 

effect of changing 127, 128 

use 4 

valve 45, 46 

Laying out valve motion 18 

Lead 33, 51 

action 4 

amount 

81, 82, 89, 99, 122, 126, 137, 177 

definition 4 

effect 3 

exhaust 33, 34, 36 

finding 21, 23, 27 

for setting valves 155 

of low-pressure valve, condensing 

engine 125 

of low-pressure valve, non-con- 
densing engine 125 

on bottom end, low-pressure 

valve side 139 

steam 34 

valve showing 98 

Linear advance of eccentric 11 

Link, details 107 

in valve gear 103, 104 

Low-pressure eccentric, adjustable. . . 139 

adjusting 137 

valve 135 

back platen 137 

setting 126,135 

side showing lead 

on bottom end. 139 
side showing lead 
on top end 137 

Mcintosh & Seymour engine 84 

Main valve, action 46, 48 

in position 49 

of Meyer combination .38, 39 
setting 101 

Marks on valve seat 59 

stems 101 

Maximum admission openings 101 



PAGE 

Maximum opening 36 

port opening 124 

travel of valve 167 

Meyer cut-off valve 38 

Minimum travel of valve 168 

Multiported cut-off valve 45 

valve 46, 76, 84, 97 

Negative exhaust lap 10 

lap, definition 11 

Nickel, F. F 180 

Non-condensing engine, lead of low- 
pressure valve 125 

Opening, maximum 36 

Outlet valve 65, 68 

Outside lap 31, 32 

Period of admission 13 

finding 14 

Piston, position 6, 7, 8, 9 

finding 26 

valve 96 

Buckeye 100 

engine 121 

engines, table showing 
effect steam lap, ex- 
haust lap, travel and 

angular advance 128 

Platen of low-pressure valve 135, 137 

Plates, pressure 107, 108 

Plock, John L 53 

Plug, valve 64, 65 

Plumbing wrist plate and rocker arm . 58 
Point of admission. .21, 33, 34, 35, 36, 124 

of compression 34, 35, 36 

finding 23 

of cut-off. .4, 15, 18, 34, 35, 36, 

40, 41, 42, 43, 44, 99, 124 
Corliss engines. . . .56, 57 

finding 22, 24 

of exhaust 17 

release 18, 34, 35, 36, 40, 71 

finding 23 

Port opening, maximum. . .^ 124 

steam, width 34 

width 37 

Porter- Allen engine 103 

Porter fly-ball governor 106 

Position of eccentric .. .41, 45, 46, 51, 176 
changing 43 



INDEX 



207 



PAGE 

Position of valves 41 

Positive exhaust lap 10 

Pressure, cylinder 96 

equalizing in exhaust pipes. 181 

plates, details 107, 108 

zero point 185 

Pump, duplex 180 

Putnam engine 130 

valve gear 129 

Radius, eccentric, changing 20 

Reach rod, length 58 

Regulator, Putnam engine 130, 132 

Release, point of. . 18, 23, 34, 35, 36, 40, 71 

"Reliance" engines 156 

Reynolds (1890) and girder frame 

Corliss engines 152 

long-range cut-off 1 72 

Rice & Sargent engine 145 

Riding cut-off valve 38 

Rites inertia governor 135, 143 

Rice & Sargent 

engines 149 

Rock shaft 134 

Rocker arm 94, 171 

plumbing 58 

Rod, angle, finding 16 

correcting for angle of 17, 18 

cut-off, adjusting 150 

dashpot, length 58, 59, 154 

eccentric, length. .42, 73, 75, 170, 171 

too long 72 

exhaust valve, length 60 

governor, adjusting 60 

length 46 

reach, length 58 

test for proper length 101 

valve, length 168 

Safety stop, setting 82 

Seats, valve 88 

Separate steam and exhaust valves ... 113 

Setting blowing-engine valves 198 

eccentric 102 

engine at half stroke 51 

exhaust valve 81 

high-pressure valve 138 

main valve and eccentric .... 101 

piston valves 100 

safety stop 82 



PAGE 

Setting steam valves 74, 108 

suction valve 194 

valves 29, 46 

Brown engine 79 

Buckeye engine 97 

Fitchburg engine. . .117, 119 
Fleming piston - valve 

engine 121 

Greene-Wheelock en- 
gine 73 

horizontal Corliss steam 

engines 54 

Mcintosh & Seymour 

engine 89 

Porter-Allen engine. . . . 109 

Putnam engine 130 

Reynolds long - range 

cut-off 177 

Rice & Sargent engine. . 147 

Wright engine 168 

Shaft governor, action 119 

Side shaft, diagram 131 

Slide valve 3 

D 19 

Speed of valve motion 41, 42 

Steam, admission 40 

and cut-off, Meyer 

cut-off valve 39 

chest, valves removed 49 

engines, Corliss 53 

lap 4, 31, 32 

effect of changing 127, 128 

use 4 

lead 34 

port, width 34 

pressures, Corliss engines . . .56, 57 

valve 113, 114 

balanced 115 

equalizing movement. . . 82 

motion 115 

open at both ends when 

hooked up 174 

operation 76 

setting 74, 108 

Steam, exhaust valve, length 81 

valve, length 170 

marks 101 

Stroke, adjusting 89 

events, determining 124 

measuring 91 

Sturtevant compound engine 135 



208 



INDEX 



PAGE 

Sturtevant compound engines, details 
and meas- 
urements. . . 144 

Suction air valve, opening 188 

valve, setting 194 

Table of laps and lead for setting 

valves 155 

showing effect of changing 
steam lap, exhaust lap, 
travel and angular advance, 

for piston- valve engines 128 

Tandem compounds, valve setting. . . 125 

Templets for valve setting 122 

Test for proper length of rods 101 

Tipping motion of link 104 

Travel 101 

direction 41 

effect of changing 127, 128 

horizontal, of pin 97 

of crank 41 

of eccentric 70 

of valve. .32, 34, 36, 39, 41, 42, 
46, 70, 74, 84, 95, 97, 
114, 117, 165, 167, 

168, 170 

adjusting 73 

changing 20 

finding 22, 23, 26, 27 

Trip cam 68 

Trouble, causes 72 

Trunnions, position 110 

Valve action 6, 175 

Meyer combination 39 

adjusting Ill, 117 

for lap 75 

and steam passages, sectional 

view, Putnam engine 132 

arrangement in cylinder 161 

balanced. .93, 96, 103, 113, 115, 135 

chest 93, 94 

circle 30 

cross-exhaust 181 

cut-off 95, 97 

position. 99 

cylinder, details 107 

D slide 19 

diagram, use 21, 30 

double-ported 97, 156 

equalizing movement 81 



Valve exhaust 68, 113 

adjusting 75 

setting 81, 148 

flat 93, 96, 103 

gear 103, 196, 198 

air compressor 191 

Buckeye engine 92, 93 

centralization, double ec- 
centric engine 61 

Fitchburg engine Ill, 112 

Greene- Wheelock engine . . 64 

operation 146 

Putnam engine 129 

gridiron 62, 84, 88, 159, 161 

high-pressure 138, 140 

Hill 62 

inlet 65, 67 

lap 45, 46 

low-pressure 135 

main, action 46 

adjusting action 48 

in position 49 

Meyer cut-off 38 

motion Ill, 113 

laying out 18 

speed 41, 42 

movement 87, 159, 164 

multiported 76, 84, 97 

operation 85 

outlet 65, 68 

piston 96, 100 

plug 64, 65 

position 41 

corresponding to given 

crank position 30 

riding cut-off 38 

rods, length 168 

seats 88 

seat, marks 59 

setting 29, 46 

Brown engine* 79 

Buckeye engine 97 

double eccentric engine . 

60, 61 

effects of changing 19 

Fitchburg engine. . .117, 119 
Fleming piston - valve 

engine 121 

Greene-Wheelock engine 73 
horizontal Corliss steam 
engines 54 



INDEX 



209 



Valve setting, Mcintosh & Seymour 

engine 8'J 

« Porter- Allen engine 108 

Putnam engine 130 

Reynolds long - range 

cut-off 177 

Rice & Sargent engine. . 147 

Wright engine 168 

showing lead 98 

slide 3 

steam 113, 114 

equalizing movement. ... 82 
open at both ends when 

hooked up 174 

operation 76 

setting 74 

stems, length 1 70 

marks 101 

suction, opening 188 

travel. .4, 10, 11, 32, 34, 36, 39, 
42, 70, 73, 74, 84, 95, 
97, 114, 117, 165, 167, 

168, 170, 185, 188 
changing 20 



PAfUO 

Valve travel, finding 22, 23, 26, 27 

with and without lap. ... 4 

Volume, zero point 1S5 

Volumetric efficiency of compressor. . 188 

Wedge adjustment for keying up ])iu 

bearings 1 20 

Wheelock arrangement of valves .... 62 
Wright automatic cut-off engine, view 

of exhaust side KiO 

automatic cut-off engine, view 

of steam side 158 

steam engine 159 

William 159 

Wrist plate. .154, 157, 161, 162, 164, 

168, 178, 191, 199, 201 

centering 170 

central marks on hub .... 59 

in extreme position 59 

plumbing 58 

Zero point of pressure and volume. . . 185 
Zeuner slide-valve diagram 23, 29 



NOV IB leos 



